The fauna and geography of the Maldive and Laccadive ...

Q 

115 

.F38 

v.l 

pt.3 

Part IV. of Vohmie I. will be published on 

Jamiary 75, /90J. 

The Fauna and Geography 

of the 

Maldive and Laccadive Archipelagoes 

Being the Account of the Work carried on and 

of the Collections made by an Expedition 

during the years 1899 and 1900 

J. 

Edited b y 

Stanley Gardiner, M.A. 

Fellow of Gonville and Caius College and late Balfour Student 

of the University of Cambridge. 

VOLUME I. PART III. 

With Plates XIV—XVII and Text-Illustrations 41—75 

Cambridge : 

at the University Press. 

London : 

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J. Clay and Sons, 

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The Fauna and Geography 

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VOLUME I. PART III.

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Being the Account of the Work carried on and 

of the Collections made by an Expedition 

during the years 1899 and 1900 

J. 

Edited by 

Stanley Gardiner, M.A. 

Fellow of Gonville and Caius College and late Balfour Student 

of the University of Cambridge. 

VOLUME I. PART III. 

With Plates XIV—XVII and Text-Illustrations 41—75 

Cambridge : 

at the University Press. 

1902 

(.

CAMBKIDGE 

PRINTED BY J. AND C. P. CLAY, 

AT THE UNIVERSITY PRESS. 

:

Reports. 

CONTENTS OF VOL. I. PART III. 

1. The Actinogonidiate Echinoderms of the Maldive and Laccadive 

Islands 223 

By Prof. F. Jeffrey Bell, M.A. 

2. Orthoptera 234 

By Malcolm Bdrr, F.Z.S., etc. 

3. Marine Crustaceans. III. The Xanthidae and some other Crabs. 

With Text-Figs. 41—60 ........ 237 

By L. A. BORRADAILE, M.A. 

4. On the Fishes from the Maldive Islands. I. Dredged. II. Fresh- 

water 272 

By C. Tate Regan, B.A. 

5. The Marine Tiubellaria, with an Account of the Anatomy of 

some of the Species. With Plates XIV and XV and Text- Figs. 

61—73 282 

By Frank Fortescue Laidlaw, B.A. 

6. The Maldive and Laccadive Groups, with Notes on other Coral 

Formations in the Indian Ocean [continued). With Plates 

XVI and XVII and Text-Figs. 74 and 75 . . . . 313 

By J. Stanley Gardiner, M.A.

THE ACTINOGONIDIATE ECHINODEKMS OF THE 

MALDIVE AND LACCADIVE ISLANDS. 

By F. Jeffrey Bell, M.A., Emeritus Professor and Fellow of King's College, 

London. 

By the kindness of Mr Stanley Gardiner I have had the opportunity of examining the 

Echinoderms collected by him in the Maldive and Laccadive Islands. The collection is 

of the ordinary coral-reef tj'pe, and consists, as did that from the Macclesfield Bank (see 

Proc. Zool. Soc. London, 1894, p. 392), very largely of young forms; these are, of course, of 

very great value and interest, more, I think, than any number of " new species," but they 

make no show in a systematic report. When a study is made of the changes that occur 

during post-larval gi-owth these specimens will be seen at their full value. There are a large 

number of Ophiuroids, and some would probably, if determined, require describing as " new 

species"; since 1888, however, we have known of 132 (or 120) species of Ophiuroids from 

the Indo-Pacific area (see Brock, Zeitschr. 

f. 

wiss. Zool. xlvii. p. 538) ; .since then I and others 

have helped to swell the list, but, so far as I know, no one has done anything to codify or set 

in order the numerous so-called species, based, many of them, on one or a few specimens, and 

often so described as to be quite misleading. I have not thought it my duty on this occasion 

to swell the list. On the other hand, just as in the Bassett Smith collection, I was able to 

detect the rare and interesting Ophiopteron elegans, so in the Stanley Gardiner collection I 

have found the very rare Ophiaethiops nnicolor described by Brock in the journal just cited. 

As I have also found 0. elegans in some quantity I am able to point out that Brock's statement 

as to the poverty of the western forms of the Indo-Pacific, as compared with the eastern, 

requires some modification. 

Lastly, there is a point which is of far wider interest than the discovery of new species 

in these variable forms ; again and again on working through the Ophiuroids I have observed 

that the upper surface of the disc has disappeared. I can only again urge on those who 

are for a time staying near a reef to investigate the problem which I raised in 1888, and 

which, to his regret (see Tijds. Nederl. Dierk. Ver. v. (1898), p. 306) was not known to Dr Sluiter 

till ten years later. It is clear that, if the gonads of an Ophiuroid be set free by the separation 

of the disc, and if a new disc be formed and new gonads developed, the question of germ- 

plasm may be considered settled. 

I have endeavoured as on some previous occasions (see especially P.Z.S. 1887, p. 523) to 

avoid the treatment at inordinate length which appears to be a real joy to many naturalists 

G. 29 

;

224 F. JEFFREY BELL. 

I have given a systematic list of the species with references sufficient to make clear what 

is meant, and aid in any further research that it may be desirable to make ; the nature of 

the bottom is stated, and in many cases the frequency or rarity of the species is mentioned. 

CRINOIDEA. 

I. Genus Antedon. 

Immature forms—not identifiable—were dredged on 10 occasions, sometimes in considerable 

numbers, between 19 and 37/ (fathoms), and a few were also secured by diving off the west 

reef of Hulule. They seem to especially frequent the inner ends of the passages, where they 

embouch into the lagoons; in all cases the bottom is recorded as having rubble or coral, with 

perhaps sand or weed. 

1. Antedon laevissima. 

Comatula laevissima Grube, J.B. Schles. Ges. liii. (1875), p. 74. 

Antedon laevissima, P. H. Carpenter, Chall. Rep. Comat. (1888), p. 197. 

I still hope to be able to obtain the late Dr P. H. Carpenter's notes on Grube's 'type.' 

Dredged eight times in seven atolls between 20 and 37/., usually from a hard sand or 

shell bottom \vith some weed. In one dredging, 37 /., in the middle but just within the 

N. passage of Suvadiva, some adults and thousands of the immature forms of this species of 

Crinoid— and no other—were obtained. 

p. 564. 

2. Antedon milherti. 

Comatula (Alecto) milherti, Midler, MB. Akad. Berl. 1846, p. 178. 

Antedon milherti, P. H. Carp. Chall. Rep. Comat. (1888), p. 194. 

Suvadiva, 43/, sand, strewn with dead oyster shells. 

3. Antedon palmata. 

Comatula {Alecto) palmata, Mtiller, Physik. Abhandl. Akad. Berlin, 1847 (1849), p. 261. 

Antedon palmata, P. H. Carp. Chall. Rep. (1888), p. 226. 

Kolumadulu, 38/, mud and weed, and Mulaku, 40/, weed, fine sand and rubble. 

4. Antedon indica. 

Comatula indica, E. A. Smith, Ann. Mag. XVII. (1876), p. 406; Phil. Trans. 168 (1879), 

Antedon indica, P. H. Carp. Chall. Rep. (1888), p. 225. 

From the west reef of Hulule, Male Atoll, among corals. 

5. Antedon variipinna. 

Antedon variipinna, P. H. Carp. J. Linn. Soc. Lond. XVI. (1882), p. 506 ; id. Chall. Rep. 

(1888), p. 256, ihique citata. 

S. Nilandu, 19/, at the seaward end of a passage, living corals.

ACTINOGONIDIATE ECHINODERMS. 225 

II. Genus Actinometra. 

Younsr forms were obtained off the coral masses of the west reef of Hulule. It is 

noticeable that neither this genus nor Antedon was found in the lagoon nor on the reefs of 

Minikoi. 

6. Actinometra typica. 

Phanogenia typica, Lov6n, Ofv. Vet. Akad. Fork 1866, p. 231. 

Actinometra typica, P. H. Carp. op. cit. p. 296. 

Suvadiva, 42/., hard sand. 

7. Actinometra fimhriata. 

Comatula fimhriata, Lamk. Anim. s. Vert. ii. (1816), p. 534. 

Actinometra fimhriata, P. H. Carp. op. cit. p. 317 ; Hartlaub, Nova Acta Leop. Carol. 

Akad. LViii. (1891), p. 102. 

Dr Hartlaub has already called attention to a specimen which he referred to this species, 

part of which was, in the terminology of Carpenter, bi-, and the other part tri-distichate. 

Several specimens in the present collection exhibit the same striking peculiarity; in 1894 

{P.Z.S. p. 398) I adduced evidence against the value of the syzygy as a specific character; now 

doubt is thrown on the safety of the number of the distichals. 

From the western reef-edge, Hulule, and dredged six times in five atolls, 24—35/, rubble 

or sand, mud or weed. 

8. Actinoynetra multiradiata. 

Asterias multiradiata, Linn. Syst. Nat. (1758), p. 663. 

Comatula inidtiradiata, Lamk. Anim. s. Vert. II. (1816), p. 533. 

Actinometra multiradiata, Duj. and Hup6, Echinodermes (1862), p. 210 ; P. H. Carp. Chall. 

Rep. (1888), p. 322. 

Hulule, 15— 20/., from slope of western reef, hard bottom. 

9. Actinometra sentosa. 

Actinometra sentosa, P. H. Carp. op. cit. p. 325. 

N. Male, 25 and 27/., coral masses and coarse sand. 

10. Actinometra maculata. 

Actinometra maculata, P. H. Carp. op. cit. p. 307. 

From the west reef of Hulule, and very commonly seen at shallow depths on lagoon reefs 

in all the more open atolls of the Maldives. 

29—2


11. Acanthaster echinites. 

ASTEROIDEA. 

III. Genus Acanthaster. 

See the synonyms given by Prof. Peirier in Arch. Zool. expir. iv. (1875), p. 361, and the 

observations of M. de Loriol, in Mem. Soc. Pliys. et d'hist. nat. de Genlve, xxix. no. 4 (1885), 

pp. 6 et seq. 

From the sand flat to the north-west of Hiilule. 

IV. Genus Linckia. 

A number of young forms collected one night in the swabs, when at anchor in N. Male, 

25/!, rubble, Polytreina and sponges. 

12. Linckia laevigata. 

Asterias laevigata, Gmelin, Syst. Nat. (1788), p. 3169. 

Linchia laevigata, Llitken, Videnskab. Meddel. 1871, p. 47. 

From the boulder zone of the reef at Minikoi only. 

13. Linckia multiforis. 

Asterias multiforis, Lamk. Anim. s. Vert. iii. (1816), p. 254. 

Ophidiaster multiforis, M. Tr. Syst. Aster. (1842), p. 31. 

Linckia midtiforis, von Mai-tens, Arcli. f. Naturg. xxxil. (1866), p. 65. 

Common on every reef of the Maldives, especially frequenting the shaded under-surfaces of 

stones of the boulder zone. Large numbers were attracted at Minikoi to a baited basket 

placed under a stone, after 24 hours no less than 37 specimens being collected. 

14. Scytaster variolatus. 

V. Geniis Scytaster. 

Asterias variolata, Retzius, Diss. spec. Aste?; (1805), p. 19. 

Scytaster variolatus, M. Tr. Syst. Aster: (1842), p. 34. 

S. Nilandu, 25/., with corals, sponges and Alcyonarians, and Mulaku, 25, 30 and 35/., all 

mud and a little weed. 

15. Scytaster novae-caledoniae. 

Scytaster novae-caledoniae, Perrier, Arch. Zool. exper. iv. (1875), p. 426. 

Found on all the sand-flats in the Maldives and Minikoi. In colour it is generally brown 

or blue; most forms at Minikoi were blue, while five specimens from Hulule were all brown. 

16. Ophidiaster cylindricus. 

VI. Genus Ophidiaster. 

Asterias cylindrica, Lamk. Anim. s. Vert. ill. (1816), p. 255.


Ophidiaster cylindricus, M. Tr. Syst. Aster. (1842), p. 29. 

A regular denizen of the boulder zone of every reef visited in the Maldives, also at 

Minikoi. See Dr Mac Munn's Note on the pigment of this species, pp. 

of this publication. 

VII. Genus Retaster. 

189—90, Vol. i. Part ii. 

The genus was represented by a few immature forms from Mahlos, 23/., and Mulaku, 30/, 

sand and rubble. 

17. Mithrodia clavigera. 

VIII. Genus Mithrodia. 

Asterias clavigera, Lamk. Anim. s. Vert. ii. (1816), p. 562. 

Mithrodia clavigera, Perr. Arch. Zool. exper. iv. (1875), p. 378. 

Suvadiva, 30/., across the inner end of a passage, hard bottom. 

18. Fromia milleporella. 

IX. Genus Fromia. 

Asterias inilleporella, Lamk. Anim. s. Vert. ii. (1816), p. 564. 

Fromia inilleporella, Perr. Ai-ch. Zool. exper. iv. (1875), p. 437. 

A single specimen found under the overhanging side of a growing coral near the edge 

of the east reef of Naifaro, Fadifolu. 

19. Asterina cepheiis^. 

X. Genus Asterina. 

Asteriscus cepheus, M. Tr. Syst. Aster. (1842), p. 41. 

Asterina cephea. Pen-. Arch. Zool. exper. v. (1876), p. 235. 

Fadifolu, 15 /, from a passage covered with coral growth, and from the outer reef off 

Maradu, Addu. Immature forms are common on the Maldive reefs, but only the single above- 

mentioned adult was obtained. The 3'oung cling to the rock of the reef-flat or boulder zone, 

and do not seek cover in the daytime as do most species. 

XI. Genus Pentagonaster. 

Two immature forms were dredged from 35/, Kolumadulu, dead, and broken shells. 

XII. Genus Stellaster. 

Young specimens from 30/, S. Nilandu, hard sand, corals and sponges, and 40/, Mulaku, 

weed, sand and rubble. 

20. Stellaster incei. 

Stellaster incei. Gray, P7-oc. Zool. Sac. Lond. 1847, p. 76. 

Pentagonaster {Stellaster) incei, Perr. op. cit. V. p. 43. 

Dredged three times in different atolls, 23—30/, sand and rock. 

^ Some writers say cephea, but, as any astronomer will tell them, cepheus is a star, and was the name of a Greek king.


XIII. Genus Astropecten. 

Immature forms from 40/., Suvadiva, broken corals and nullipores, and Halimeda, and 

34/., Felidu, sand covered with weed. 

21. Astropecten polyacanthus. 

Astropecten polyacanthus, M. Tr. Syst. Aster. (1842), p. 69. 

Dredged five times in four atolls, 19—38 /, hard bottom with corals, or mud with weed 

and sponges (Mulaku). 

22. Astropecten iiidicus. 

Astropecten indicm, Doderlein, Zool. JB. Syst. iii. (1888), p. 828. 

Suvadiva, 40/, fine mud. 

23. Luidia macidata. 

XIV. Genus Luidia. 

Luidia maculata, M. Tr. Syst. Ast. (1842), p. 77. 

S. Nilandu, 19/, seaward end of a passage. 

OPHIUROIDEA. 

XV. Genus Ophiocoma. 

Large numbers of immature specimens are obtained on breaking up decaying corals and 

under beach sandstone masses between tide marks. They are sometimes also found in sponges. 

24. Ophiocoma erinaceus. 

25. Ophiocoma scolopendrina. 

In 1887,1 wi-ote (Scient. Trans. Roy. Dublin Soc. III. (1887), p. 648), "It is almost certain 

that in a short time systematists will be agreed as to the necessity of uniting these two 

species of Ophiocoma." In 1888 the late Dr Brock (Zeitschr. f. wiss. Zool. XLvn. (1888), 

p. 495), said, " Es ist wohl jetzt kein Zweifel mehr, dass beide Arten vereinigt werden miissen." 

Fifteen years' further experience only confirms me in this view. 

The form called 0. erinaceus is characteristic of the reefs of Minikoi and all parts of 

the Maldives wherever there is decaying coral rock. It was dredged also with dead coral 

rubble off a shoal in Suvadiva, 25/ The second form, 0. scolopendrina, was only found at 

Minikoi, where it is numerous under stones on the reef to the east of the island. 

26. Ophiocoma valenciae. 

Ophiocoma valenciae, M. Tr. Syst. Ast. (1842), p. 102. 

A regular species of the boulder zone in Minikoi and all parts of the Maldives. 

27. Ophiocoma brevipes. 

Ophiocoma brevipes, Peters, A7xh. f. Nat. 1852, p. 85. 

On every p.art of the reefs of Minikoi and the Maldives, but especially numerous under 

beach sandstone masses.

sand-flat. 

28. Ophiomastix annulosa. 


XVI. Genus Ophiomastix. 

Ophiomastix annulosa, M. Tr. Syst. Ast. (1842), p. 107. 

Minikoi only, common in the boulder zone. 

29. Ophiomastix venosa. 

Ophiomastix venosa, Peters, Arch. f. Naturg. 1852, p. 83. 

Common in the Maldives, at Hulule a regular form in and under coral masses on the 

XVII. Genus Ophionereis. 

An immature specimen from Kolumadulu, 22 f., sand and rubble. 

30. Ophionereis porrecta. 

Ophionereis porrecta, Lyman, Proc. Boston Soc. iV. H. VII. (1860), p. 260. 

Dredged three times in different atolls, 24— 35/., coral, rubble or hard bottom. 

XVIII. Genus Ophiothrix. 

Immature forms—often very numerous—in 11 dredgings, 22—46 f., usually sand with 

some rubble, but in the deepest fine, hard mud. 

31. Ophiothrix aspidota. 

Ophiothrix aspidota, M. Tr. Syst. Ast. (1842), p. 115. 

Suvadiva, 20/., across the inner end of a passage, hard bottom. 

32. Ophiothrix nereidina. 

Ophiura nereidina, Lamk. Anim. S. Vert. ii. (1816), p. 544. 

Ophiothrix nereidina, M. Tr. Syst. Ast. (1842), p. 115. 

Minikoi and Maldives, under corals of reef-flat. 

33. Ophiopteron elegans. 

XIX. Genus Ophiopteron. 

Ophiopteron elegans, Ludwig, Zeitschr. f. wiss. Zool. XLVII. (1888), p. 459. 

Dredged five times in 3 atolls, 22—35 f, in every case near passages, hard bottom, 

perhaps rubble and weed. 

34. Ophioaethiops unicolor. 

XX. Genus Ophioaethiops. 

Ophioaethiops, Brock, Zeitschr. f. wiss. Zool. xlvii. (1888), p. 524. 

This is the most interesting of Mr Gardiner's finds, as, with the exception of the three 

specimens found at Amboina by Brock, the species is unknown. I had little doubt as to 

the identity of the creature, but to make sure I submitted it to Prof. Ehlers of Gottingen,


who compared it with the originals. As Brock remarked that Ophioaethiops was closely allied 

to Dr Marktanner-Turneretscher's Ophioluphus I was glad of the opportunity afforded me by 

Dr von Marenzeller of comparing the two. I confess I was struck by the differences between 

them. 

In a hole of a coral mass from the reef of Naifaro, Fadifolu. 

35. Astrophyton clavatum. 

XXI. Genus Astrophyton. 

Astrophyton clavatum, Lyman, Proc. Boston Soc. N. H. vin. (1861), p. 85. 

Mahlos, 24 f., dead and living corals, and Suvadiva, 38/., coarse shell and coral fragments. 

36. Cidaris metularia. 

ECHINOIDEA. 

XXII. Genus Cidaris. 

Cidarites metularia, Lamk. Aîim. S. Vert. ill. (1816), p. 56. 

Cidaris metularia, A. Ag. Rev. Ech. (1872), p. 98. 

Found constantly on every part of all the reefs visited, wedged in between the branches 

of growing corals. Dredged five times with corals, 20—25/. 

corals. 

37. Diadema saxatile. 

XXIII. Genus Diadema. 

Echinus saxatilis, Linn. Syst. Nat. (1758), p. 664. 

Diadema setosum, auct. plurim. 

Diadema saxatile, Loven, Bih. Sven. Vet. Akad. Hdlgr. 13, iv., no. 5 (1887), p. 135. 

Found on every reef under stones or in hollows of the boulder zone, or between growing 

38. Echinothrix diadema. 

XXIV. Genus Echinothrix. 

Echinus diadema, Linn. Syst. Nat. ed. x. (1858), p. 664. 

Echinothrix calamaris, A. Ag. Rev. Ech. (1872), p. 119. 

Echinothrix diadema, Lov^n, Bih. Sven. Vet. Akad. Hdlgr. 13, iv. no. 5 (1887), p. 137. 

Both this and the next species were common in Minikoi and in the Maldives in the same 

position as Diadema saxatile. 

39. Echinothrix desori. 

Astroj>yga desori, Ag. Ann. Sci. nat. vi. (1846), p. 345. 

Echinothnx desori, A. Ag. Rev. Ech. (1872), p. 120.


XXV, Genus Astropyga. 

Immature forms, N. Male, 25/, coral masses, Polytrema, etc., and Mulaku, 30_/!, green and 

dead weed, also from Minikoi lagoon, Q f. 

40. Asthenosoma urens. 

XXVI. Genus Asthenosoma. 

Cyanosoma urens, Sarasins, Zool. Anzeig. IX. (1886), p. 80. 

Asthenosoma urens, iid. Ergeh. Forschungen avf Ceylon, i. (1888), p. 86. 

A large number of specimens, Mulaku, 27 /., mud and sponges, also Haddumati, 40 /., mud 

and weed, and Suvadiva, 43/., soft mud. 

XXVII. Genus Temnopleurus. 

Immature forms in 5 dredgings, 22—25/, sand, weed and generally rubble. 

41. Temnopleurus toreumaticus. 

Cidaris toreumatica, Leske, Addit. ad hist. p. 155. 

Temnopleurus toreumaticus, Agass. m Valentin's Avat. du gejire Echinus (1841), p. viii 

Bell, P.Z.S. 1880, p. 428. 

Mulaku, 28 /., and Haddumati, 40 /., mud and weed. 

42. Salmacis hicolor. 

XXVIII. Genus Salmacis. 

Salmacis hicolor, Agass. op. cit. p. viii. ; Al. Ag. Rev. Ech. (1872), p. 156. 

Suvadiva, 30 /"., hard sand (?), and Haddumati, 32 and 40 /., dead coral masses, mud and 

weed. The Suvadiva specimen had associated with it a similarly coloured Gastropod, which 

was resting in an especial clearing among its spines. 

43. 

Tripneustes angulosa. 

XXIX. Genus Tripneustes. 

Cidaris angulosa, Leske, Addit. (1788), p. 92. 

Tripneustes angulosa. Bell, P.Z.S. (1879), p. 657. 

Occasionally found at Minikoi and the Maldives on the sand-flats, not uncommonly cast 

up on the lagoon beaches. 

44. Echinometra lucunter. 

XXX. Genus Echinometra. 

Echinus lucunter, Linn. Syst. Nat. ed. X. (1758), p. 665. 

Echinometra lucunter, De Blainv. Actin. (1834), p. 225; Lov^n, Bih. Sv. Vet. Akad. Hdlgr. 

13, IV. no. 5 (1887), p. 153. 

Wedged into hollows in the extreme seaward edges of all reefs, almost where the rollers 

break. The animal varies rather in colour, the lighter forms occurring further out. 

G. 

30 

;


XXXI. Genus Fibularia. 

A large number of immature specimens from a velu or lagoon of one of the smaller rim 

atolls (faro) of N. Male, 5 /"., coarse sand. 

45. Fibularia volva. 

Fibularia volva, Ag. Ann. Sci. Nat. vii. (1847), p. 142; Al. Ag. Rev. Ech. (1872), p. 130. 

Mahlos, 24 /., living and dead coral. 

46. Echinoneus cyclostomus. 

XXXII. Genus Echinoneus. 

Echinoneus cyclostomus, Leske, Addit. (1778), p. 173; Al. Ag. Rev. Ech. (1872), p. 117. 

From sand under stones or coral masses on the sand-flats at Minikoi and throughout the 

Maldives. A large number of young specimens were dredged in the lagoons of Minikoi and 

Hulule, 6—8 f., these appearing to be their nurseries. The young shells were never found 

alive on any surface reef, but they are a regular constituent of sandy beaches. 

weed. 

XXXIII. Genus Laganum. 

Immature forms dredged 6 times, 30—36 /., hard bottom with rubble, corals, sponges and 

47. Laganum dejwessuni. 

Laganum depressum, Ag. Man. Scutel. (1841), p. 110. 

Dredged 9 times in 6 atolls, 18—38/., rubble bottom with sand, or mud and perhajDS weed. 

XXXIV. Genus Clypeaster. 

An immature specimen from a passage into S. Nilandu, 25/, corals and sponges. 

XXXV. Genus Brissopsis. 

Immature forms only, from Mulaku, 30/, sand and weed. 

A few immature specimens from Hulule. 

48. Lovenia elongata. 

XXXVI. Genus Brissus. 

XXXVII. Genus Lovenia. 

Spatangus elongatus, Gray, in Eyre, Discov. Central Austral, i. (1845), p. 436; Al. Ag. Rev. 

Ech. I. (1872), p. 139. 

Lovenia elongata, Gray, Ann. and Mag. N.H. vil. (1851), p. 131. 

Only from the sand-flat to the north of Hulule, under corals.

49. Maretia alta. 


XXXVIII. Genus Maretia. 

Maretia alta, A. Ag. (1863), see Rev. Ech. 1872, p. 139. 

Felidu, 34_/!, sand covered with weed. 

50. Maretia planulata. 

Spatangus plamdatus, Lamk. An. s. Vert. ill. (1816), p. 31. 

Small forms found occasionally at low tide level on lagoon flats everywhere. Dredged 

7 times in Kolumadulu and Felidu, 20—35/, rubble or shells and sand, also Haddumati, 40/., 

weed and mud. 

30—2

ORTHOPTERA. 

By Malcolm Burr, F.Z.S., F.E.S., F.L.S. 

The collection includes twenty-four species, of which one adult, a Liphoplus, cannot be 

identified with any known form. Almost all the others are cosmopolitan or widely distributed 

Oriental species, probably all occurring also in India or Ceylon. A few field notes have been 

added by Mr Stanley Gardiner. 

FORFICULARIA. 

1. Anisolahis annulipes Luc. Minikoi, 1 {/. 

BLATTODEA. 

2. Periplaneta americana L. Minikoi. Common throughout the Maldives, infesting the 

larger boats, but seldom found on shore. 

3. Leucophaea sunnamensis L. Minikoi, I

ORTHOPTERA. 235 

This species is abundant and widely distributed throughout the Oriental region. It is 

the commonest grasshopper in the Maldives and Laccadives, any number being caught in 

open, dry sjôts by means of the sweep-net. 

Fam. Pyrgomorphidae. 

9. Atractomorpha gerstaeckeri Bol. Minikoi, 1 ,f. 

10. Atractomorpha similis Bol. Hulule, 1 ^. 

11. Atractomorpha crenulata Fabr. Minikoi. 

Very common in the above island, frequenting the paths in the densest jungle. Much 

more numerous towards sunset. 

Fam. Acridiidae. 

12. Oxya intricata Stal., var. tihiis posticis ferrugineis. A large number of specimens 

from Minikoi, Mahlosmadulu, Miladumadulu, Goidu and Hulule. 

This form is only found in the northern part of the Maldive Group, and does not extend 

to Suvadiva and Addu. It is in no island so abundant as at Minikoi. The species frequents 

open spaces, especially the dry grain lands of Miladumadulu atoll. 

13. Acridium septemfasciatum Serv. Minikoi, 1 c/, 1 ?, not found in the Maldives. 

Fam. Tettigidae. 

14. Hedotettix gracilis Haan. Minikoi, 1 (/". 

LOCUSTODEA. 

Fam. Phaneropteridae. 

15. Phaneroptera indica Br. A number of specimens from Minikoi, Mahlosmadulu and 

Hulule. The commonest locust in the Maldives, found throughout the whole group from 

Miladumadulu to Addu. 

All the specimens appear to be referable to the above species, but are somewhat smaller 

than the dimensions given by Brunner. 

Fam. Conocephalidae. 

16. Conocephalus hreviceps Redt. Minikoi, 1 % ; Mahlosmadulu, 2 ^f, 1$. 

17. Conocephalus sp. Hulule, 1 $ larva. 

18. Xiphidium maculatum Le Gou. A number of specimens from Minikoi and the 

Maldives. 

A widely distributed Oriental species. It is very common in Minikoi, but, although seen 

in nearly every atoll of the Maldives, rare everywhere.

236 MALCOLM BURR. 

19. LipJioplus n. sp. Minikoi, 1 %. 

GEYLLODEA. 

Fam. Myrmecophelidae. 

This appears to be a new species, but I refrain from describing it as the collection 

contains but a single female, not in perfect condition. It differs from Liphoplus fasciatus Br., 

in its paler colour and larger size ; from L. novarae in its larger size and black-bordered 

elytrae ; and from L. guerinianus in its paler colour. 

20. Ectatoderus longicaitdus Sauss. Minikoi, 2 ,/, 6 $ and 4 larvae. Common in the 

roots of the grass near the lighthouse. 

I am not quite positive as to the correct identification of this species, but the genus 

is little known, and the species are not very clearly defined. The specimens from Minikoi 

approach nearer to this than any other described form. 

Fam. Trigonididae. 

21. Trigonidium cicindeloides Serv. Minikoi, 4^/', 3$ and 3 larvae. 

This species is common on the shores of the Mediterranean, and occurs also in Ceylon 

and Burmah. 

22. Homoexiphiis histrio Sauss. Minikoi, 2 $. 

23. Landreva picta Sauss. Hulule, 1 $ 

. 

Fam. Gryllidae. 

I refer the single female with some hesitation to this species. 

24. Gryllm mitratus Burm. Minikoi, 1 % ; Mahlosmadulu, 1 ? ; and Hulule, 1 /. A 

common Oriental species.

MARINE CRUSTACEANS. 

III. THE XANTHIDAE AND SOME OTHER CRABS. 

By L. A. BoRRADAiLE, M.A., Lecturer in Natural Sciences at Sehvy 

College, Cambridge. 

(With Text-figures 41—60.) 

The in-stalment of the Marine Crustaceans of the Expedition described in this paper 

includes, besides the Xanthidae, two new genera, possibly allied to them, and a couple of 

small families— the Atelecyclidae and the Hapalocarcinidae—which are taken here for reasons 

of convenience. Some remarks on the natural history of the crabs will be found under the 

headings of the families, genera, etc. to which they belong. 

Fig. 41. Types of the Xanthid Crabs. A. Actaea fossulata, resembling water-worn coral pebbles and found in the 

lower parts of a coral stock or other situations into which pebbles could be washed. B. CarpiUus exsculptus, 

adapted for passively withstanding surf and currents. C. Euxanthus exsculptus var. rugosus, found amongst stones, 

etc. on the reef. B. Chlorodius harhatus. E. Domoecia hispida, a coral crab. F. Trapezia ferruginea, also a coral 

crab. The drawings are not made to scale, i? is a large crab, C and F of moderate size, and the others small. 

Family Xanthidae. 

Of all the families of crabs the Xanthidae are the most numerous in genera and species, 

and the most varied in form, though this preeminence is seen chiefly in the Tropics, and 

there best in the littoral belt, where they are to be found in every possible position. 

")i

238 L. A. BORRADAILE. 

Morphologically, the Xanthids are characterised, among the other round-fronted crabs (Cy- 

clometopa), by the absence of a rostrum, the sloping or transverse first antennae and short 

second antennae, the sharp fore edge to the mouth, and the legs of the last pair not adapted 

for swimming, nor the branchial regions swollen. Bionomically they are harder to characterise, 

but, speaking broadly, we may say that they are not sand crabs, nor swimming crabs, nor 

land crabs, but essentially crabs of the reef surface and the coral stocks, though some of them 

may be found in other positions. Their division into subfamilies and genera depends on such 

characters as the shape of the orbits and antennae, and the relationships of these to one 

another, the ridges on the palate (endostome) which mark out the channels by which water 

leaves the gill-chamber, and the shape of the body'. The species are separated by details 

such as the shape of the front and the hands, the sculpture and areolation of the carapace, 

and the presence or absence of spines on the limbs or the sides of the body. 

The body of a typical Xanthid—a Xantho, for instance (Fig. 50), or an Actaea (Figs. 4U., 

53, 54), or Carpilius (Fig. 41 B), is of a transversely oval shape, heavy and compact, with a 

hard cuticle and short legs, which can be folded up close under the body". The chelae are 

usually large and powerful, and the habits sluggish. Such crabs live almost anywhere on 

the reef sometimes showing a preference for some particular kind of shelter, such as holes 

or cracks in the rocks, but more often, I think, adapting themselves to any that can be 

found. Specimens are thus often taken in coral stocks, though the crabs cannot be said to 

be characteristically coral crabs, being equally, if not more often, found under stones, which 

afford the most favourite hiding-place of all ; some of the larger species are restricted to 

the reef, but many of the smaller ones are also to be found in the lagoon wherever coral 

' lu the following key the sub-families of the Xanthidae 

are defined by means of these features : 

I. Endostome ridges wanting. Shape of the body trans- 

versely oval or rounded. 

A. Flagellum of antenna not shut out of orbital gap. 

1. Second joint of anteunal stalk cylindrical, reaching 

the front but not entering the orbital gap. 

Xanthiiuie. 

2. Second joint of antennal stalk as in Xanthinae but 

entering the orbital gap. 

Cdrpiliiiae. 

B. Flagellum of antenna shut out of orbital gap by part 

of the second joint of the stalk. 

Etixinae. 

n. Endostome ridges present. Shape of the body often 

square or squarish. 

A. Front less than half, and fronto-orbital edge (front 

and orbits together) not more than two-thirds the 

greatest breadth of the carapace. Front usually 

makes an arch with the anterolateral edge. Fla- 

gellum of antenna usually not phut out of orbital 

gap. 

1. Second joint of antennal stalk cylindrical, and may 

or may not reach the front, with which it is not 

below. 

broadly in contact. Endostome ridges vary in 

shape and size. 

3Ie)iippinac. 

2. Second joint of antennal stalk somewhat irregular 

in shape and broadly in contact with the front. 

Endostome ridges strong, and project on the fore 

edge of the mouth. 

Oziinae. 

B. Front at least half, and fronto-orbital edge more 

than two-thirds the greatest breadth of the cara- 

pace. Front makes an angle with the antero- 

lateral edge. Flagellum of antenna alwaj's shut 

out of orbital gap. 

1. Endostome ridges strong, and project on the fore 

edge of the mouth. 

Eiiphiijiae. 

2. Endostome ridges moderate, and make no projection 

on the fore edge of the mouth. 

Trapeziiime. 

The genera will be found ranged under these sub-families 

- The figure (41 c) of Euxanthus exsculptus gives an excel- 

lent example of the way in which the limbs are often folded 

up so as to form with the bodj' a compact mass. Fig. 47 

shows how the legs are sometimes specially shaped for folding 

into a small compass.

MARINE CRUSTACEANS. 239 

grows. The massive, compact form of body and the strong cuticle are, no doubt, adaptations 

to a life spent in positions where they are surrounded with hard, stony objects, and exposed 

at times to surf and strong currents, and at others to enemies which they are unable to 

escape by swimming like the Portunidae. 

From this typical body-form there are, of course, deviations in various directions, of 

which a few only can be mentioned here. Such genera as Chlorodius (Fig. 41 1)) and Pseu- 

dozius (Fig. 45) are flatter and lighter built, with longer legs, though the cuticle is still strong, 

and they are more often to be found in situations like the interstices of coral stocks, where 

they must maintain their position by the use of their limbs, rather than by their weight 

or by wedging themselves fast, like the heavier genera. Yet even these' are far from being 

true coral crabs, restricted to the living jjarts of the stock, like Melia (Fig. 49), Bomecia 

(Fig. 41 E), or the Trapeziinae (Figs. 41 F, 58), on which some remarks will be found below-. 

Another very characteristic habitus is that of Pilumnus (Figs. 46— 48), slightly built, very 

hairy, and often with squarish, rather than oval, bodies, falling very steeply in front. 

As to the meaning of the numerous, and often very beautiful, features by which the 

Xanthids are distinguished in detail, it is as yet impossible, in most cases, to say anything. 

Why, for instance, are the species of Actaea bejewelled with the most beautiful pearly granules 

(Figs. 53, 54) ? And why do these granules become sharp thorns in some species (Fig. 56), 

and flatten themselves into leaflets in others (Fig. 55) i Why should the back of Euxanthus 

(Fig. 41 C) be rough and uneven, or that of Carpilius (Fig. 41 B) glassy smooth ? Why is 

Liomera barrel-shaped (Fig. 52) and Pseudozius often as flat as a board (Figs. 43, 44)? 

Before these questions can be answered, much more must be known about the habits of 

the crabs. We may, however, indicate some directions in which it will be well to look 

for the answer. The texture of the back and legs, and their nakedness or hairiness, will 

perhaps be found to depend on the necessity of friction with the surrounding objects when 

the animal wedges itself firmly into its hiding-place, or of presenting a smooth surface to 

waves and currents, so that they may pass over the animal without sweeping it away; or 

again to the need of disguise, either by a covering of fine silt, held by hairs or bristles 

(often a very effectual device) or by adherent organisms which will not grow on a smooth 

surface, or even [Actaea cavipes and fossulata (Fig. 41.4)] by a likeness to water-worn pebbles 

of coral. The shape of the hands may be adapted to the food, or to defence against some 

special enemy, or—in correspondence with that of the front—to breathing among foreign 

particles of various grades of coarseness', or in some cases seems to be a sexual character. 

The remarkable hoof-like ends to the fingers (Fig. 57 C), which turn up again and again in 

different genera', may serve to give their owner a foothold among the rough coral branches, 

or may gather food in some special way, like the tufted, spoon-like fingers of the pra\vn 

Atya. The shape of the front depends on the way in which the antennae are used, and on 

the need of keeping open a way for the breathing stream, a function which it shares with 

the chelipeds''. And lastly the shape of the end-joints of the walking legs, which shows a 

' Except, probably, P. coralliophilus and P. triunguicu- than it has yet received. Another instance of it, mentioned 

latiis (p. 241 S.). below (p. 242), is the pulley arrangement at the end of the 

- pp. 249, 263. walking legs. Of course the closure of the orbital gap has 

' Garstang, Q. J. M. S. XL. p. 211. happened over and over again in various groups of Crabs, and 

' This phenomenon of the occurrence of the same feature the loss of the mandibular palp and the epipodites among 

in groups which cannot be related to one another is not Prawns is a similar case. 

uncommon among Decapods, and is worthy of more attention 

G. 31

240 L. A. BORllADAILE. 

very great diversity, will be found, I believe, to be connected with the nature of the ground 

on which the animal's life is passed, whether it live among stones or in sandy places or in 

coral stocks, and to its habits, whether it crouch with folded limbs under shelter or hold 

fast with its legs. 

Fig. 42. Ends of the walking legs of Xanthid Crabs. A. Tip of tbe end-joint in Cnrpilius convexus (Fig. 41 A). 

B. Same part in Trapezia ferruginea (Fig. 41 F). C. Whole end-joint in Actaea speciosa. The drawings are 

not made to scale, 

.-1 being much less enlarged than iS or C. 

A number of examples of this feature may be found in the illustrations scattered through 

the present paper, but in the accompanying figure (Fig. 42) three of the most unlike of 

them are shown enlarged. Carpilius convexus is a heavy-bodied, spindle-shanked crab, too 

big and clumsy to climb among the branches of coral stocks, which leads a sluggish and 

uneventful life among objects on the bottom, and has even been found enclosed as in a 

cage by the growth of coraP. Its legs {A) accordingly end in a very simple claw. Trnpezia 

ferruginea is a typical crab of the living coral, and we may suppose that the remarkable 

ending of its legs (B) is in some way connected with this fact. But what can be the 

meaning of the curious brush of hairs at the end of the first walking leg of Actaea 

speciosa (C), and why this structure is not found on the other legs, cannot as yet be even 

guessed. Some remarks on the different ways in which the last joint may be hinged on 

to that before it will be found below on p. 242. 

According to Henderson [Tr. Linn. Soc. Zuol. (2) V. p. 332] the colour markings of shore 

Decapoda are generally protective in their nature, but this is certainly not always the case, 

as, f)r instance, in Trapezia and Carpilodes. 

In another respect, besides those of structure and habits, the Xanthids offer a contrast 

to the swimming crabs, described in the last number of this publication, which, next to 

them, are the most conspicuous family of crabs in the Tropics. They are, with some striking 

exceptions, not very variable, and are not varietal, save in a few cases. In the Trapeziinae, 

however, varieties appear, and the genus Piliimnus shows a remarkable plasticit}' of constitu- 

tion, which leads to the formation of numerous local species and will be alluded to again 

below ^ 

1 Coutiere, Bull. Mas. hist, iiat., 1898, 5, p. 238. - P- 244.

with age. 

1. Pseudozius dispar Dana, 1852. 


Subfamily Menippinae. 

Genus Pseudoziiis Dana, 1851. 

Pseudozius dispar, Caiman, Tr. Linn. Soc. (2) viii. p. 14 (1900)i. 

The granular field on the larger hand of the male of this species grows relatively smaller 

Taken on the reef in Male, Goifurfehendu and Fadifolu Atolls, and in Funadu Vein, 

Miladumadulu Atoll. 

2. Pseudozius caystrus (Ad. and Wh.), 1848. Alcock, ill. p. 181. 

This very common species, which is recorded by Alcock from the Laccadives, almost 

certainly occurs at Minikoi, though unfortunately no specimens of it have reached England-. 

b 

Fig. 43. Limbs of Pseudozius coralliophilnx; a. outside of greater haud, l>. walking leg, c, d. end of the same enlarged. 

3. Pseudozius coralliophilus, n. sp. (Fig. 43). 

— 

Diagnosis : " A Pseudoziiis with the carapace finely granular, bearing a few scattered hairs, 

the regions faintly marked out ; the front sloping gradually downwards, cleft into two low, 

rounded lobes, the fuiTow between the front and the orbit ending on a small lobe ; the antero- 

lateral edge with three very low humj)s, from the last of which a fine ridge runs inwards 

on the back; the chelipeds unequal, finely granular, their fingers widely gaping, especially on 

the large hand, furrowed and subcylindrical, with a few isolated blunt teeth, the arm and 

wrist (meropodite and carpopodite of the cheliped) without spines, the fore edge of the arm 

finely toothed ; and the walking legs fairly stout, with a long end-claw. 

Length : 3 mm. Breadth : 4 mm. Colour in spirit : cream, with pale brown, cream-tipped 

fingers. 

A single male specimen was taken from a block of the brain-coral Leptoria tenuis growing 

in the lagoon at Minikoi. It was sheltering at the bottom of one of the holes in the coral 

made by another little crab Cryptochirus coralliodytes^. Whether the first owner of the hole 

had died, or left willingly, or had been ousted by the Pseudozius there was nothing to show, 

nor can we tell as yet whether the latter lives always in Cryptochiru,s-h.o\es or had merely 

retreated into one in this case as the water drained off the surface of the coral. In another 

of these holes there was found a female Pseudozius, sheltering in the same way, and it was 

^ Wbere synonyms will be found. For the principle on - See footnote to p. 191 of Part II. of this publication, 

which references are given in this paper see p. 192 of Part II. 

of the present publication. 

'' 

See below, p. 271. 

" 

31—2


natural to suppose at first that this was the female of the crab whose male we have just 

described. Further examination, however, showed differences between the two so great that 

they must belong to different species. The second specimen is described below under the name 

of P. triunguiculatus. 

I am much obliged to Mr Edwin Wilson, F.E.S., for calling my attention to a very in- 

teresting structure which he discovered on the legs of this crab (Fig. 43 b— d). As usual, the 

last joint (dactylopodite, end-joint) is held in a deep notch at the end of the one before it 

(propodite). But in the present case it bears on the hinder side a flange, and on the flange 

a knob, which works in a groove on the propodite. At the inner end of this groove is a 

small pit, into which the knob slips when the joint is fully flexed, so that the end-joint is 

held firm in this position, thus providing the crab with a hook, by which, no doubt, it keeps 

its position on the coral. P. triunguiculatus has a less perfect form of the same apparatus 

(Fig. 44 c). In it, the flange on the last joint works against a special process of the one before 

Fig. 44. Pseudozius truingtiiculatits, symbiotic with a coral; a. whole animal, b. outside of greater hand, 

c. hinder side of end of walking leg, d. fore side of the same. 

it, but this process has only a smooth surface and no gi-oove. A small spine under the pro- 

podite seems placed in this position to prevent the end-joint from being unduly flexed, and 

no doubt the other spines give a foothold to the animal. On the whole, these structures, as 

well as the general appearance of the body and limbs, give the impression that the crabs are 

indeed symbiotic with the coral, living always on its surface, but take refuge in the Crypto- 

chirus holes at times only. 

Interestingly enough, the same structure, in its simpler form of a flange on the end-joint 

working along a smooth path on the joint before it, turns up again in the coral crabs of the 

Trapeziinae and in Domecia, though not in Melia, which crooks the whole leg and not the 

last joints only, and is also present in Chlorodopsis (Fig. 57 c) and Phymodius, which, without


being true coral crabs, are often found in coral stocks, and in the Actaeas of the flosculata- 

gi'oup, of whose habits as yet nothing is kno\vn, since they have only been taken with the 

dredge. Actaea speciosa (Fig. 42 O) is an example of a species in which the flange is not 

found. The object of the apparatus is, no doubt, to enable the end-joint to be moved more 

evenly and accurately and held fast in any position ; and it is only an elaboration of structures 

found in most crabs, which have usually a small facet on the hinder side of the last joint for 

the end of the propodite. Its absence is, nevertheless, particularly interesting in the case of 

Eriphia, which is allied to Doniecia, and of Pseudozius other than the two species mentioned 

above. A single glance at the orbits of these latter species is enough to show that they have 

no place among the Trapeziinae, Eriphiinae, or Etisinae, so that the formation of the legs in 

question must have arisen, like so many other chai-acters of the crabs, independently in two 

or more cases^ It is probably an adaptation to clambering. 

4. Pseudozius triunguiculatus, n. sp. (Fig. 44). 

Diagnosis : " A Pseudozius with the carapace flat, smooth (microscopically roughened) and 

hairless, the regions not marked out ; the front sloping slightly downwards, standing well forward 

beyond the eyes, with a wide shallow bight instead of the usual notch in the middle, no side 

lobes, and a shallow median furrow ; the anterolateral edge with three low, blunt teeth, the 

hindermost of which is hardly distinguishable ; the chelipeds, large, unequal, covered with granules 

of some size, which are largest on the upper part of the outside of the hand, no spines on the 

arm or wrist, the fingers flattened, not gaping, sharply pointed at the tips, in the large hand 

the fingers set, on their opposed edges, with a row each of conical teeth, in the small hand 

these edges blade-like, making up a remarkable pair of shears, which are no doubt adapted 

to some peculiarity in the habits ; and the walking legs rather slender, each bearing on its 

last joint a set of three slender, brown end-claws, of which two are somewhat smaller than 

the third." 

Length : 3 mm. Breadth : 

4 

mm. Colour in spirit : pale brown, the walking legs white, 

the back covered with small dark-brown spots, the fingers white. 

One female specimen taken on Leptoria tenuis in Minikoi lagoon. 

Subgenus Platyozius, n. 

A specimen dredged in Suvadiva cannot be refeiTed to any known species, and is also 

difficult to place in a genus. It differs from Pseudozius, as hitherto defined, in more than one 

point, but none of these is of importance enough to warrant the setting up of a new genus, 

and it is therefore taken here as the type of a new subgenus Platyozius. Other groups of 

species akin to Pseudozius will probably have to be reduced to this rank before long. 

Platyozius differs from Pseudozius s. str. in the following points: (1) Relatively greater 

fronto-orbital breadth. (2) Absence of small outer lobes from the front. (3) Equality of the 

chelipeds. (4) Slenderness of the legs. (.5) A flatter and shallower body. (6) Less marked 

endostome ridges. 

5. Pseudozius {Platyozius) laevis, n. sp. (Fig. 45). 

Diagnosis : " A Platyozius with the carapace smooth, hairless, without regions ; the front 

broad, bent slightly .downward, almost straight, with a broad shallow bight in the middle and 

1 See above, footnote to p. 239.


notches separating it from the orbits, but no outer lobes ; the anterolateral edges short, with 

two big blunt triangular teeth behind the orbital angle, and a small notch, rather than a pro- 

jecting tooth, at the junction with the posterolateral edge ; the hinder edge slightly hollowed 

the chelipeds equal, smooth, without spines but with a blunt tooth at the inner angle of the 

Fig. 45. Pseudozins laevis; a. whole animal, b. outside of hand. 

wrist, the fingers compressed, grooved, not gaping, each with a row of triangular teeth inter- 

locking with those of the other; and the walking legs long, slender, sparsely hairy, and with- 

out spines, except on the dactylopodite of the last leg, which is rather broad, while those of 

the other walking legs are very long and narrow." 

Length : 5 mm. Breadth : 6 mm. Colour in spirit : white. 

One male specimen dredged in 20 fathoms in Suvadiva Atoll. 

Genus Pilumnus, Leach, 1815. 

As a general rule the species of crabs are not local in distribution, but are spread over 

wide areas and are probably correlated with habitative ' rather than geographical diiferences 

in environment. There are, of course, exceptions to this rule, as for instance the land and 

freshwater crabs of the genera Sesarma and Potamon. Pilumnus is another of these excep- 

tions, as may be seen at once on looking down a list of the known species, when it will be 

evident that many of them have been only recorded from one locality. This impression is 

strengthened on reading the remarks of various authors in recording a species from a new 

locality. In many cases the identification is doubtful, or the description does not tally with 

that of the original specimens. The present collection affords an excellent example of this, 

not one of the 11 species being represented by specimens which exactly obey former diagnoses. 

Under the circumstances I shall describe as new species the forms which do not agree 

closely with specific de.scriptions already published, and rank as subspecies'- those which in- 

' For the meaning of this word, see p. 195 of Part II. of 

this publication. 

- See footnote to p. 195 of Part II. of this publication. 

;


fringe such descriptions in small points only. The phenomenon of local variation in Pilumnus 

deserves, and would repay, careful investigation, especially with regard to the existence of 

intermediates, their number relative to those of the described forms, and their distribution, 

whether they be found in intermediate localities or no. In short, information is needed as 

to whether the subspecies of Pilumnus be " discontinuous," like true varieties, or no. 

The members of the genus live under stones, in coral blocks, etc. 

6. Pilumnus vespertilio (Fabr.) 1793. Alcock, III.' p. 192. 

The fur of the Maldive specimens is not dark, as in the type, but of a golden-yellow 

colour, like that of Alcock's Karachi and Tavoy race. At the same time the usual smooth patch 

is to be found near the base of the finger of the large hand. Perhaps these characters are 

distinctive of local races or subspecies of P. vespertilio. 

The species, which is sluggish in its habits, lives under stones, etc., and was taken on 

the reef at Hulule, Male Atoll, and in Funadu Velu, Miladumadulu. 

7. Pilumnus andersoni de Man, 1887. subsp.^ See Alcock, ill. p. 194. 

The Maldive specimens differ from the race defined by Alcock in the following points 

(1) There are no granules on the carapace, which is everywhere smooth and finely pitted. 

(2) The spines on the fore edge of the meropodites of the walking legs are vestigial, and 

there is no spine at the end of the joint. (3) The arrangement of the spines on the fore 

edge of the arm does not agree with that described by de Man. Alcock does not mention 

these spines, but, as he cites de Man's paper, it is presumable that all his specimens presented 

the same arrangement as the type. In the Maldive example there is a row of strong, blunt 

teeth, growing smaller from without inwards. In de Man's specimens there were two, large, 

arched, sharp spines at the outer end, with a small spine at the base of the distal of the 

two. The more proximal was larger than the distal one, and behind it were four or five 

acute granules. 

Dredged in .5—39 fathoms in Minikoi, South Nilandu, and Haddumati Atolls. 

8. Pilumnus hirsutus Stimps, 18.58. subsp. See Alcock, in. p. 197. 

The Maldive specimens differ from those on which Alcock's description was founded in the 

following points: (1) A small subhepatic tooth is present. (2) The gaps on the orbital edge 

are fairly distinct. 

According to Haswell {Cat. Austral. Crust, p. 69), the meropodites of the walking legs of 

this species should bear three or four spines. Alcock does not mention these spines, and they 

are wanting in the Maldive specimens, in which the fore edge of the meropodite is roughened 

by a row of low, blunt teeth. Alcock is doubtful about the identity of the species he is 

describing as P. hirsutus, and it seems likely that the three forms ' are -distinct. 

A single specimen from South Nilandu, which bears a Sacculina, differs from the others 

in the following points : (1) The antennal flagella are long and hairy. (2) 'The large hand 

is rather less " full." (3) The body is rather flatter. (4) The legs are a little longer. 

' Journ. As. Soc. Beng. lxvii. ii. pp. 67—233 (1898). For include species, subspecies, and varieties. In this sense it 

the principle on which references are given in this paper see is a useful counterpart of "group," used to include all 

Vol. I. Part II. p. 192 of the present publication. divisions of the animal kingdom from genera upwards. For 

^ See footnote to p. 195 of Part II. of this publication. definition of " variety " and " subspecies " see the article on 

' I am using the word "form" in its broadest sense to Varieties in Part II. of this publication. 

:


It is impossible to say whether any or all of these features be due to the presence of the 

parasite. 

The figure of a specimen referred to this species in the P.Z.S. for 1900 [pi. XLii., fig. 9] 

was drawn with the hair on the body and in consequence the side-teeth and frontal notch 

have not been shown by the artist. 

Dredged in 22—45 fathoms in Haddumati, Felidu, Addu, Mulaku, North Male, South 

Nilandu, Suvadiva, and Kolumadulu Atolls. 

Fio. 46. Pihimmis rottindus; a. whole animal, h. outside of hand. 

9. Pilumnus rotundus, n. sp. (Fig. 46). 

Diagnosis : " A Pihuiihus with the carapace very convex, subglobular, covered with short 

hairs, the regions faintly marked ; the lobes of the front only moderately prominent, with faintly 

granular edge ; the lower rim of the orbit denticulate, the upper rim granular, with two distinct 

but shallow notches; the anterolateral edge bearing four spiniform teeth, of which the first is 

the orbital angle, the teeth being short and set wide apart and having smaller teeth at their 

bases ; the chelipeds rather unequal, covered outside with .stout thorns, which are arranged in 

somewhat irregular rows and are largest on the upper side, the fingers bent at an angle with 

the hand, the moveable finger bearing a strong ridge above ; and the walking legs moderately 

long, covered with long hairs, and with a thorn on the upper edge of the meropodite and one 

at the end of both the meropodite and the carpopodite." 

Length: 8 mm. Breadth: 12 mm. Colour in sjiirit : yellowish-white, with white fingers. 

Dredged in 35 fathoms in Kolumadulu Atoll. 

10. Pilumnus do7-sipes Stimps, 1858. Alcock, ill. p. 197. 

The specimens agree very closely with Alcock 's definition, but I am quite unable to detect


any gi'anulation of the carapace, which, when laid bare, is absolutely smooth, save for the stumps 

of the hairs. The larger hand is very stout and the fingers short. 

The species was taken in South Nilandu, Haddumati, North Male, Mulaku, Suvadiva, Felidu, 

Kolumadulu, and Fadifolu Atolls, in 12—70 fathoms of water. 

11. Pilumnus maldivensis, n. sp. (Fig. 47). 

Diagnosis ; " A Pilumnus with the carapace convex both fore and aft and from side to 

side, smooth, pubescent and hairy, the regions faintly marked ; the middle lobes of the front 

prominent, the outer lobes very small 

; : 

the lower rim of the orbit finely ^ ^^^ 

toothed, the upper rim smooth, with 

traces of two notches ; the antero- 

lateral edge short, with three spini- 

form teeth and a spine on the orbital 

angle ; 

the chelipeds unequal, granular 

and hairy outside, a small bare patch 

at the base of the fingers and along 

the lower edge of the greater hand, 

fingers moderately long, smooth ; and 

the walking legs of moderate length 

and stoutness, hairy and pubescent, 

and without thorns on the meropo- 

dites." 

Length: 4 mm. Breadth: .5 mm. Fig. 47. Pilumnus maldiveruiis; a. whole animal, b. outside of hand, 

(Largest specimen.) Colour in spirit 

yellowish-white, fingers white. 


(1) The fore edge of the meropodites of all the walking legs bears three spines besides that 

at the end of the joint. In de Man's race there is only one, and that is wanting from the 

last leg. (2) The red colour mentioned by de Man is wholly wanting, though of course this 

may be due to the state of preservation. 

Taken in South Nilandu Atoll, in 19—25 fathoms. 

Fig. 48. Pilumnus alcocki; a. whole animal, 6. outside of hand. 

14. Pilumnus alcocki, n. sp. (Fig. 48). 

Diagnosis : 

" A Pilumnus with the carapace of moderate breadth only, covered rather sparsely 

with long hairs but without pubescence, the regions well marked ; the front almost straight, slightly 

arched, not deeply notched in the middle, bearing a fringe of very long hairs ; the anterolateral 

edge raised into three low mounds, the hindermost of which is very inconspicuous ; the outer 

orbital notch shallow, the inner wanting, the lower orbital rim granular, the orbital angle not 

at all jjrominentj the chelipeds subequal, granular and covered with long hairs, the fingers 

gaping, somewhat furrowed and toothed ; and the walking legs short, stout, hairy and pubescent, 

and without thorns on the meropodites." 

Length : 4-8 mm. Breadth : 6-2 mm. Colour in spirit : white. 

Dredged in 20 fathoms in Suvadiva Atoll. 

I have called this species after Major A. Alcock, F.K.S., to whose excellent work ofi the 

Indian Crabs it has so often been necessary to refer in the present paper. 

15. Actumnus globosus (Dana), 1852. 

Genus Actumnus Dana, 1851. 

Pilumnus glubosus, Dana, U.S. Expl. Expd. Crust, i. p. 236, pi. xii. fig. 10 (1852). 

By the shape of its body this species seems to belong to Actumnus, rather than to


Pilmnnus, though, in any case, with A. obesus Dana, 1852, and A. elegans de Man, 1887, 

it holds an intermediate position. 

Taken on the reef at Minikoi. 

16. Actumniis setifer (de Haan), 1835. Alcock, iii. p. 202. 

The carapace is very sparsely granular in the larger specimens. 

Dredged in 23—30 fathoms in Mahlos and South Nilandu Atolls. 

17. Actumnus tomentosus Dana, 1852. Alcock, iii. p. 202. 

Dredged in 25 fathoms in South Nilandu Atoll. 

Genus Melia Latr., 1825. 

I have followed Ortmann in placing this genus provisionally in the Menippinae chiefly 

because the orbital gap forbids its being included in the Trapeziinae, to which its body-shape, 

coral haunting habits, and coloration seem at first to show a relationship. For the rest, the 

shape of the body may be reached without much difficulty from that of Pilumnus, and none 

Fig. 49. Melia tessellata, bearing in its claws two sea anemoues. The colour of this crab in life is very beautiful 

Its translucent legs are ringed, as in the figure, with dark purple, and lines of the same colour mark out the 

body into polygonal fields which are coloured pale pink or brown and lemon yellow. The anemones when alive 

are olive-green, and the coral pink or green. The whole figure is considerably enlarged, and b, which shows the 

"hand" holding an anemone, is very much so. 

of the other characters offers any great obstacle to our classifying it with the present sub- 

family. It has obviously undergone considerable modifications in structure in connection with 

its peculiar and interesting habits. 

32—2

250 L- A. BORRADAILE. 

18. Melia tessellata (Latr.) (Fig. 49.) 

Melia tessellata, Borradaile, Pi-oc. Zool. Soc. 1900, p. 580. 

This crab, which lives, like Trapezia, among the living branches of coral stocks, holding 

on by its long slender legs, has for some time ' been known to be in the habit of carrying 

in each chela a small sea anemone. The object of this habit is not known, but it is certainly 

a voluntary act on the part of the crab, for the actinian is not attached, but held between 

the fingers of the Melia, and, if it be taken away, will be again seized. Usually there is an 

anemone in each hand, but sometimes one or both hands are empty. The actinians, which 

are grasped firmly round the middle below the tentacles, may be useful, by means of their 

stinging-cells, either for defence or to " fish " for food with, or perhaps for both purjjoses. 

The chelipeds are slender and feeble—ill-suited for defence, but at the same time mobile and 

well adapted to wield the anemones they carry, and, if the crab be threatened, it will stretch 

out its arms towards the aggressor, as thovigh it would ward him off with the disagreeable 

obstacles it thus presents to his attack. Certainly the fingers cannot be used to take food 

unless the anemone be first dropped, but, on the other hand, the tentacles of the latter are 

directed outwards, away from the mouth of the crab. The third maxillipeds are mobile, with 

the proximal joints rather slender and the last three stout, and are ft-inged with long hairs. 

Possibly they are used to catch small organisms for food in much the same way as those of 

the China Crabs (Porcellanidae), which part with their chelipeds so readily when they are 

attacked, since they do not use them for taking food. 

In any case we seem to have here an interesting example of the use of an implement 

by an animal which, however intelligent, has at least a very differently organised nervous 

system from the Vertebrata. It should be noted that the case is different from that of a spider 

crab, which sticks pieces of seaweed on its back and enjoys passively the concealment gotten 

thereby. For the Melia carries the anemone in its cheliped—the chief grasping organ of the 

animal, corresponding to the hand of a primate or the trunk of an elephant—and, what- 

ever its use, it cannot be a means of passive concealment, to which its size is wholly inade- 

quate-. 

Melia tessellata is not recorded from the Indian region by Alcock, who finds the genus 

represented there by two quite distinct new species {M. caesti/er and M. pugil). It would be 

interesting to know the precise distribution, geographical and habitative, of these three species. 

The " hairs " mentioned by Alcock as found on the fingers of his new species may possibly 

be the remains of actinians, rotten from bad jjreservation, and in that case it would be needful 

to determine whether each species of crab has its own species of anemone. Of course we 

must also know whether the latter be full grown or only young individuals. The species was 

taken on the reef in Male, Addu, Minikoi and Goifurfehendu Atoll. 

Subfamily Xanthinae. 

Genus Cymo de Haan, 1833. 

The members of this genus live under stones, in coral blocks, etc. 

' The fact was noted in 1880 by Richter (Mobius' Meeres- ments to fasten together the edges of the leaves which form 

fauna Mauritius), but since then its interest, and indeed its its home, holding them, the while, in its jaws. There is also 

Tery existence, have been generally overlooked. said to be a wasp which uses a stone to beat down the earth 

^ The aut Oecophylla smaragdina uses its own larvae over its burrow, 

(which haTe glands for making a cocoon) as spinning imple-


19. Gymo andreossyi (And.) 1826, var. inelanodactyliis (de Haan) 1833. Alcock, in. j). 174. 

Taken on the shore in Minikoi and Goifurfehendu Atolls, and dredged from 12 fathoms 

in Fadifolu Atoll. 

20. Gymo quadrilobatus, Miers, 1884. Alcock, ill. p. 17.5. This species is probably 

identical with G. tuhercidatus Ortmann {Zool. Jahrb. vii. Syst., p. 443). 

Taken on the shore in Male, Goifurfehendu and Fadifolu Atolls. 

Fig. 50. Xantho frontalis ; a. whole animal, 6. outside of hand, c. underside of meropodite of walking leg, to show 

21. Xantho frontalis, n. sp. (Fig. 50). 

the groove into which the last three joints can be folded. 

Genus Xantho Leach, 1815. 

Diagnosis : " A Xantho with the whole body finely and evenly granulated, the regions 

marked out by fine sharp lines ; the front prominent, its outline like that of a cupid's bow 

the anterolateral edge divided into four lobes, of which the first two are low and rounded and 

the last two prominent and conical ; the chelipeds subequal, their outer surface rough and 

uneven, the hands with four indistinct longitudinal ridges, the fingers furrowed and bearing 

interlocking teeth, the upper side of the hand with an irregular-rounded lobe, the inside of the 

wrist with a conical tooth ; and the walking legs short, with long end-joints, two knobs on the 

upper side of the carpopodite, and a hollow under the meropodite into which the outer joints can 

be folded." 

Atolls. 

Length : 5 mm. Breadth : 8 mm. Colour in spirit : white with pale-brown fingers. 

Genus Xanthias Rathbun, 1897. 

22. Xanthias lamarcki (H. M. Edw.), 1834. Alcock, in. p. 157. 

Taken on the shore in Male, Goifurfehendu, Miladumadulu, Fadifolu, S. Mahlos, and Minikoi 

;


23. Xanthias notatus (Dana), 1852. Alcock, in. p. 1.58. 

Taken on the reef and in the lagoon at Minikoi. 

Genus Leptodius, A. M.-Edw., 1863. 

The numbers of this genus may be taken under stones and in coral stocks. 

24. Leptodius nudipes (Dana), 1852. Alcock, in. p. 121. 

Taken on the shore in Male, Goifurfehendu and Minikoi Atolls; in the latter locality from 

coral mass on the outer reef. 

25. Leptodius sanguineus (H. M.-Edw.), 1834. Alcock, in. p. 119. 

Taken on the shore in Goifurfehendu Atoll. 

Fig. 51. Leptodius cristatus; a. whole animal, b. outside of hand, c. end of walking leg. 

26. Leptodius (Xanthodius) cristatus, n. sp. (Fig. 51). 

Diagnosis: "A Xanthodius %vith the carapace flat behind, falling steeply in front, somewhat 

sparsely gi-anular all over, the granules being smaller and closer set in the hinder part, and naked, 

the forepart of the carapace divided upi by wide, smooth grooves ; the front bent strongly down- 

wards, with an almost straight, thickened, granular edge and a rather shallow notch in the middle 

the notches in the orbital rim indistinct ; four low side-teeth with thickened, granular edges 

the hind edge of the carapace slightly hollowed ; a feeble ridge on the endostome reaching the 

fore edge of the mouth ; the basal joint of the antenna short ; the chelipeds unequal, granular 

all over except on the facet against the body, the hands with a crest and a smooth furrow above, 

the fingers deeply hoofed at the tip, a little granular at the base, furrowed on the smaller hand 

only, with a few blunt teeth on the larger hand ; and the walking legs finely granular, their 

last two joints hairy; the carpopodite and propodite with a crest and a broad smooth groove above." 

;


Length : 5 mm. Breadth : 7 mm. Colour in spirit : mottled purple and orange-brown, 

fingers dark-brown with paler tips. 

Four female specimens were found under stones on the inner part of the reef-flat at Minikoi. 

Genus Lioxantho Ale, 1898. 

27. Lioxantho as-peratiis Ale., 1898. Alcock, iii. p. 92. 

The specimens agree exactly with Alcock's definition, excejit in not having hair on the 

dactylopodites. 

Taken on the shore at Hulule, Male Atoll. 

28. Lioxantho tumidus, Ale, 1898. Alcock, in. p. 91. 

Taken on the shore in Male and Goifurfehendu Atolls. 

29. Lioxantho punctatus (H. M. Edw.), 1834. Alcock, iii. p. 91. 

Taken on the shore at Hulule, Male Atoll. 

Genus Liomera Dana, 1851. 

30. Liomera cinctimana (White), 1847. Alcock, III. p. 88. 

Taken on the shore at Goidu, Goifurfehendu Atoll. 

Fig. 52. Liomera spinipes; a. whole animal, b. outside of band. 

31. Liomera spinipes, n. sp. (Fig. 52). 

Diagnosis : " A Liomera with the carapace smooth and polished, without a trace of regions, 

rather more than half as long as broad ; the front divided into two well-marked rounded lobes 

of simple outline ; the anterolateral edge sharp, almost crest-like in its hinder half, with traces 

of the last two lobes only, not marked off by a tubercle from the posterolateral edge ; the orbital 

i-im without notches; the antennal flagellum rather longer than the breadth of the orbit; the fore edge


of the third maxilliped ahiiost straight ; 

the chelipeds stout; the arm short and broad, with a large 

tooth near the end of the vipper edge and the lower edge roughened; the outside of the wrist 

roughened in parts; the outside of the hand covered with small, shai-jj thorns, and some of the 

same thorns on the base of the moveable finger; the fingers compressed, toothed on their opposite 

edges, and furrowed outside; and the walking legs having the upper edge of the meropodites 

much compressed and finely toothed, but not crested; the lower edge of the last meropodite 

with long thorns, those of the other meropodites with much smaller thorns, and the caqjopodites 

and propodites of all the legs rather sparsely hairy, with broad upper sides covered with prickles." 


Dredged in 30 fathoms in Mulaku Atoll. 

Genus Actaea de Haan, 1833. 

32. Actaea tomentosa (H. M.-Edw.), 1834. Alcock, iii. p. 140. 

Taken on the reef in Male, Goifurfehendu, Addu, and Minikoi Atolls. 

33. Actaea affinis (Dana), 1852. 

Actaea affinis, Borradaile, Proc. Zool. Soc, 1900, p. 583. 

Taken on the reef in Male, Goifurfehendu, Fadifolu, and Minikoi Atolls. 

34. Actaea rufopunctata (H. M.-Edw.), 1834. Alcock, in. p. 142. 

One very small female dredged in N. Male was vnthout the fine felt between the lobules 

of the back. 

Taken on the shore in Goifurfehendu Atoll, and dredged in Minikoi, North Male, and Miladu- 

madulu Atolls. 

35. Actaea upeciosa (Dana), 1852. Alcock, in. p. 143. (Fig. 42 C.) 

The first walking leg of this crab bears an organ which seems not to have been noticed 

hitherto. A brush of stiff yellow bristles surrounds and hides the end-claw on the last joint of 

the limb. What can be the use of this structure it is hard to see, but so definite and constant 

an organ must correspond to some feature in the habits of the crab. 

Taken on the reef in Male, Goifurfehendu, and Fadifolu Atolls. 

36. Actaea ruppelli (Krauss), 1843. Alcock, in. p. 144. 

The specimens are not so hairy as Alcock's definition indicates. A. Milne-Edwards says 

that the species is " legerement j)oilue." Probably the amount of hair depends greatly on the 

state of preservation of the specimens, in this as in other Xanthids. 

Taken on the reef in Goifurfehendu Atoll. 

37. Actaea lata, n. sp. (Fig. 53). 

Diagnosis: "An Actaea with the carapace broad (length : breadth = about 7 : 10) and 

strongly lobulated all over, though the lobules are not very convex, the grooves between the 

lobules smooth and lined with fine dark pile, the lobules covered with pearly granules, which 

are smaller on the hinder lobules than on those before them, long golden-brown hairs and


shorter black bristles arising among the granules, the front bent strongly downwards, not much 

arched or very strongly notched in the middle 

line ; the anterolateral edge with four low lobes, 

the first being confluent with the orbital angle 

the orbit with two notches in its upper rim 

and one in the lower; the under side of the 

body furred, and grooves running from between 

the lobes of the edge over the finely granular 

pterygostome; the posterolateral edge not marked 

by a row of granules ; the chelipeds subequal, 

the wrist and hand lobulated above, the hands 

swollen, rounded and covered with granules out- 

side and inside, the fingers short, much arched, 

not compressed or hollowed at the tip, with a 

few blunt teeth on the opposed edges and some 

granules at the base of the moveable one, which 

is furrowed, though not to the tip; and the 

walking legs covered with granules, hairs and 

bristles like those of the carapace and with a 

furrow on the hinder side of the cai-popodite." 

Length : 7 mm. Breadth : 

10 

mm. Colour 

in spirit : white with red spots ; the fingers black 

with white tips, the black spreading over a great 

part of the inner and outer sides of the palm. 

; 

fr^Sp^ 

The species is allied to A. Mrsutisdma (Ruppell), 1830, and A. kraiissi Keller, 1861, but 

may be distinguished firom both by the shape of the hands. 

Dredged in 15 fathoms in Fadifolu Atoll. 

Fio. 53. Actaea lata; n. whole animal, 0. outside of hand. 

Fio. 54. Actaea variolosa ; a. whole animal, 6. outside of hand. The animal is drawn rather broader than 

it actually is. 

G. 83

. probably 


38. Actaea variolosa, n. sp. (Fig. 54). 

Diagnosis: "An Actaea whose length is about three-quarters of its breadth; the carapace 

egg-shaped, its areas numerous but separated by shallow grooves on the fore-part, wanting behind, 

the whole surface, except the bottom of the grooves in the fore-part, covered with rounded granules, 

which are largest in the branchial region and are interspersed with stout, golden-brown bristles 

the front bent strongly downwards, prominent, fairly deeply notched in the middle ; four in- 

distinct side-lobes; the chelipeds equal, granular; the hands rather large, somewhat swollen, 

nearly square ; the fingers very short, rounded, smooth save for a few small granules on the base 

of the moveable one, each with but one tooth, which is very blunt and lies quite at the base 

where it is almost hidden by tufts of strong hairs ; and the outer surface of all the walking legs 

covered with gi-anules like those of the cheliped but with no dimples." 

Length : 6 mm. Breadth : 8 mm. Colour in spirit : white, bases of fingers black. 

The species is allied to A. obesa A. M.-Edw., 1865, but differs in the shape of the hands. 

Taken on the shore in Male Atoll. 

39. 1 Actaea pulchella A. M.-Edw., 1865. Alcock, in. p. 140. 

The specimen which I have with some doubt assigned to this species has a' very distinct 

coloration of mottled white and orange-yellow. As in Milne-Edwards's figure {Nouv. Arch. Mas. 

Hist. Nat. I., PI. XVII., fig. 5), it is only the first of the side lobes of the carapace that can be 

described as indistinct, though both Milne-Edwards and Alcock apply this term to all of them. 

If Milne-Edwards's figure be not correctly drawn, then my specimen represents another, and 

a new species. 

Dredged in 25 fathoms in North Male Atoll. 

40. Actaea gramdata (And.), 1825. Alcock, in. p. 151. 

Dredged in Haddumati, Fadifolu, Mahlos, and South Nilandu Atolls, in 19—50 fathoms. 

In two cases taken in coral stocks (one alive, one dead). Possibly it lives in such positions, rather 

than under stones. 

41. Actaea flosculata Ale, 1898. Alcock, in. p. 151. 

Taken on the reef in Miladumadulu and dredged in Suvadiva and South Nilandu Atolls, 

in 19—38 fathoms. One of the South Nilandu specimens is noted to have come from a block 

of Pocillopora. Neither this nor the species akin to it seem suited to an exposed life. 

42. Actaea spinosissima n. sp. (Fig. 55). 

Diagnosis: "An Actaea nearly akin to A. flosculata, but with the following differences 

from that species: (1) Only the spines on the back have the characteristic petaloid shape. 

Those at the sides and on the limbs are sharp thorns. (2) The posterolateral edge of the 

back is not marked by a row of small beads, as in A. flosculata and in A. perspinosa (see 

below). (3) The hinder edge has a thickened rim, which is wanting in the above-mentioned 

two species, and the whole arrangement of the tubercles on the field behind the post-gastric 

;


furrow is different, as will be seen by comparing the figures. (4) The peculiar tubercles on 

Fig. 55. Actaea splnosissinia ; a. whole animal, b. outside of hand, c. end of walking leg enlarged. 

the outside of the hand of A. fimcidata are replaced in A. spinosissima by sharp thorns, and 

the teeth on the apposed edges of the fingers are less stout." 

Length : 

4 

mm. Breadth : 5-2 mm. Colour in spirit : white. 

Dredged in Mahlos Atoll, in 23 fathoms. 

43. Actaea perspinosa, n. sp. (Fig. 56). 

Diagnosis : " An Actaea nearly akin to A. Jlosculata, but differing from it in that, in place 

of the characteristic petaloid spines 

of the latter species, it is covered 

with stout, sharp thorns of an en- 

tirely different shape." 

From A. spinosi'ssinia it differs 

in the points indicated above, and 

from A. acantha A.-M. Edw., 1861, 

and A. hystrix Miers, 1886, in the 

gi-eater size and smaller number of 

the spines. 

Length: 4 mm. Breadth: .55 mm. 

Colour in spirit : pure white. 

Dredged in Miladumadulu Atoll 

in 25 fathoms. 

44. Actaea fossulata (Girard), 

1859. Alcock, III. p. 148. (Fig. 41 A.) 

a 

"^) 

Fig. 56. Actaea perspinosa ; a. whole animal, b. outside of hand, 

c. end of walking leg enlarged. 

The bridge across the hollow on the carpopodites of the walking legs is not always to be found. 

Taken on the reef at Hulule, Male Atoll, and in Funadu Velu, Miladumadulu. 

33—2


45. Actaea cavipes (Dana), 1852. Alcock, ill. p. 147. 

Dredged in the lagoon at Minikoi, in 7—9 fathoms. 

Genus Daira de Haan, 1833. 

46. Daira perlata (Hbst.), 1790. Alcock, iii. p. 155. 

Taken on the shore in Minikoi and Goifurfehendu Atolls. 

Genus Lophozozymus A. M.-Edvv., 1863. 

47. Lophozozymus dodone (Hbst.), 1801. Alcock, iii. p. 108. 

Dredged in 4 fathoms in Male Atoll. 

Genus Zozimtts Leach, 1818. 

48. Zozimus aeneus (Linn.), 1764. Alcock, iii. p. 164. 

Taken on the shore in Male and Minikoi Atolls. 

Genus Lophactaea A. M.-Edw., 1862. 

49. Lophactaea anaglypta (Heller), 1861. Alcock, in. p. 102. 

Taken on the reef at Hulule, Male Atoll. 

50. Lophactaea cristata A. M.-Edw., 1865. Alcock, in. p. 100. 

Taken in Funadu Velu, Miladumadulu Atoll. 

51. Lophactaea fissa Henderson (1893). Alcock, in. p. 103. 

Alcock seems to have overlooked the fact that, besides the wide gaps in the side edge 

of the carapace, this species is separated from L. granulosa by the presence of a thick coating 

of long yellow hairs. No doubt because this coating hides the granules of the carapace it is 

not shown in Henderson's figure (Tr. Linn. Soc. Zool. 2. v., pi. XXXV. fig. 8), though he de- 

scribes it. 

Taken on the reef at Goidu, Goifurfehendu Atoll. 

52. Lophactaea granulosa (Rlippell), 1830. Alcock, ill. p. 101. 

Dredged in Felidu and South Male Atolls. 

53. Lophactaea semigranosa (Heller), 1861. Alcock, in. p. 101. 


Genus Atergatis de Haan, 1833. 

54. Atergatis floridus (Rumph). Alcock, in. p. 98. 

Taken on the reef at Hulule, Male Atoll, under stones.

(1898). 


Subfamily Carpilinae. 

Genus Phymodius A. M.-Edw., 1863. 

5.5. Phymodius ungulatus (H. M.-Edw.), 1834. 

Phymodius ungulatus, Ortmann, Zool. Jahrb. Syst. vii. p. 464 (1893); Alcock, ill. p. 162 

Phymodius monticulosus, Alcock, ill. p. 163 (1898). 

I am quite unable to distinguish between these species, or to assign my specimens to 

either of them rather than to the other. All the characters vary, as it seems independently, 

and the descriptions given by several authors do not always agree. Until examination of a 

long series of full-gi-own males have shown whether there exist varieties corresponding to the 

above two names, and if so exactly in what points they differ, I prefer to follow Ortmann in 

joining the species absolutely, without keeping varietal names. 

These crabs, which were taken on the reef in Hulule and Goifurfehendu Atolls and in 

lagoons in 3—7 fathoms in Minikoi and Miladumadulu Atolls, live in coral stocks and under 

stones. 

56. Phymodius sculptus (A. M.-Edw.), 1873. Alcock, iii. p. 164. 

Taken on the reef in Male and Goifurfehendu Atolls. 

Genus Chlorodius H. M.-Edw., 1834. 

The members of this genus are often found in coral stocks. 

57. Chlorodius laevissimus Dana, 1852. Alcock, iii. p. 161. 

In one specimen the teeth on the inner side of the fingers are wanting in the small chela 

and obsolescent in the large. The colour of many specimens is yellow, rather than white. 

Taken on the reef in Goidu and Fadifolu Atolls, and dredged in South Nilandu and 

Mahlos Atolls in 22—25 fathoms. 

58. Chlorodius barbatus Borradaile, 1900. (Fig. 41 D.) 

Chlorodius barbatus, Borradaile, Proc. Zool. Soc. 1900, p. 587, pi. xli. fig. 4 (1900). 

Taken on the reef, and in lagoons down to 9 fathoms, in Minikoi, Goifurfehendu, and 

Miladumadulu Atolls. 

59. Chlorodius niger (Forsk.), 1775. Alcock, iii. p. 160. 

Taken in Male, Fadifolu, Goifurfehendu, Felidu, North Male, and Minikoi Atolls on the 

reef and in lagoons down to 25 fathoms. 

Genus Euaanthus Dana, 1851. 

60. Euxanthus exsculptus (Hbst.), 1790; var. rugvsus Miers 1884. (Fig. 41 C.) 

Euxanthus melissa, Alcock, in. p. 110. 

Since Miers speaks of a specimen of some size, it is likely that this is at least a variety,

260 L. A. BORKADAILE. 

and not merely a young form. I am inclined to think that it will prove to be a distinct 

species. The specimen before me measures 14 mm. in length and 21 in breadth. The brown 

colour of the fingers does not spread over the palm. Taken on the reef at Hulule, Male Atoll. 

Genus Garpilodes Dana, 1851. 

61. Caiyilodes stimpsoni, A. M.-Edw., 1865. Alcock, ill. p. 82. 


62. ? Garpilodes pediger Ale, 1898. Alcock, ill. p. 83. 

Two small male specimens in the collection may either be the young of this species or 

belong to G. ruber. The colour is that of G. pediger. They were dredged in Miladumadulu 

and Fadifolu Atolls in 20 and 23 fathoms respectively. 

63. Garpilodes ruber A. M.-Edw., 1865. 

Garpilodes ruber, A. Milne-Edwards, Norm. Arch. Mus. p. 228, pi. xi. fig. 4 (1865). 

Dredged in 25 fathoms in South Nilandu Atoll. 

64. Garpilodes vaillantianus (A. M.-Edw.), 1862. Alcock, III. p. 85. 

Taken on the reef in Male and Goifurfehendu Atolls, in Funadu Velu, Miladumadulu, and 

in Minikoi lagoon. In the latter locality a specimen was found among the leaflets of the 

Halimeda-weed, where its bright red colour could not be in the least protective. 

65. Garpilodes monticulosus A. M.-Edw., 1873. Alcock, iii. p. 86. 

This species, which lives under stones, was taken on the reef at Male, Goifurfehendu, and 

Minikoi Atolls. 

66. Garpilodes pallidus Borradaile, 1900. 

Garpilodes pallidus, Borradaile, Proc. Zool. Soc. 1900, p. 586, pi. XL. fig. 1. 

This species is allied to G. monticulosus and to G. cariosus. It differs from the former in 

that: (1) There is no narrow transverse ridge behind the mesogastric lobule. (2) The furrows 

of the carapace are not so deep. (3) The colouring is quite different. 

From G. cariosus it differs in that: (1) The lobules are not pitted, and the carapace has 

therefore not a worm-eaten appearance. (2) There is no transverse ridge behind the mesogastric 

lobule, and the branchial lobules are not broken up into smaller ones. (3) The furrows 

between the lobules are rather shallow. (4) Counting the groove which marks off the meso- 

gastric lobule and that which runs within the hinder edge, there are altogether three grooves 

behind the lobule in question, but the middle of the three is shallow, and may consist of 

two separate dimples, hardly connected across the middle line. (5) The notch between the 

first two lobules of the edge may be rather indistinct. (6) The pink colour of the legs does 

not tend to orange (as in most of my specimens of G. cariosus), and even in the most brightly 

coloured specimens there is no trace of colour on the carapace. 

Taken on the reef at Hulule, Male Atoll.

67. Carpilodes cariosus Ale, 1898. Alcock, iii. p. 86. 


The colour in most of my specimens is not pink but orange-yellow \ One small male from 

Miladumadulu, however, exactly agrees with Alcock's description of the colouring, and at the 

same time differs from the yellow-marked specimens in having less extensive patches of colour 

on the back, and in that the lobules of its carapace are somewhat more compact and less 

irregular in shape. It is possible that this is the true C. cariosus, while the other specimens 

belong either to a distinct species or to a variety. 

Dredged in Miladumadulu, Suvadiva, Mahlos, Fadifolu, Male, and South Nilandu Atolls, 

in 20— 40 fathoms. 

Genus Carpilius Desm., 182.5. 

68. Carpilius maculatus (Linn.), 1764. Alcock, III. p. 79. 

This species was seen both at Minikoi and in the Maldives. It may be found wedged 

into holes on the reef just above low water-mark, exposed to the full force of the surf 

69. Carpilius convexus (Forsk.), 1775. Alcock, iii. p. 80 (Fig. 41 B, 42 A). 

Taken in Fadifolu, Male, Minikoi and North Male Atolls on the reef and in lagoons down 

to 35 fathoms. 

Subfamily Etisinae. 

Genus Chlorodopsis A. M.-Edw., 1873. 

70. Chlorodopsis spinipes (Heller), 1861. Alcock, iii. p. 169. 

Taken on the reef in Male and Minikoi Atolls. 

71. Chlorodopsis woodmasoni Ale, 1898. Alcock, in. p. 171. 

Taken on the reef in Male, Fadifolu and Goifurfehendu Atolls, and dredged in 6 fathoms 

in Male Atoll. 

72. Chlorodopsis frontalis (Dana), 1852. 

1 Etisodes frontalis, Dana. U.S. Expl. Expd. Crust, i. p. 187, pi. IX. fig. 3 (1852). 

[Not Etisodes frontalis, Bori-adaile, P7'oc. Zool. Soc. 1900, p. 588 (1900) = Leptodius sanguineus 

H. M.-Edw., 1834, juv.] 

The collection contains specimens of a crab which resembles Dana's species in all but the 

following points: (1) The forepart of the carapace derives its roughness, not from minute 

granules, but from minute dimples. (2) The carapace is a little broader than in Dana's figure. 

(3) The chelipeds are not entii-ely " unaiTned," for the wrist bears two blunt teeth on the inside. 

The front and the upper edges of the legs of the last four pairs are finely toothed. The 

fore edge of the meropodite of the third maxilliped is but slightly hollowed. The length of 

the carapace is very little more than f of the breadth. 

I have placed this species in the genus Chlorodopsis because the fronto-orbital breadth is 

a little mo7-e than half the greatest breadth, and because of the outline of the fore edge of 

the meropodite of the third maxilliped. The front is not broad enough to justify its being 

1 C. vailliantianus also often tends to orange rather than crimson, when preserved in spirit.

262 L- A. BORBADAILE. 

placed in the subgenus Cyclodius, being less than half the breadth of the carapace. In any 

case the species seems to be a transitional one. 

The specimens mentioned under the name of this species in the P. Z. S. for 1900 were 

small individuals of Leptodius sanguiiieus. 

Taken on the reef on Male Atoll and dredged in 25 fathoms in South Nilandu Atoll. 

Fig. 57. Chlorodopsis espinosus; a. whole animal, b. outside of hand, c. ends of fingers to show hoof-like tips, 

d. end of walking leg enlarged. 

73. Chlorodopsis espinosus, n. sp. (Fig. 57). 

Diagnosis : " A Chlorodopsis whose length is just under f of the breadth, the carapace 

hairless, of even surface but minutely granular, areolated as in C. frontalis (Dana) ; the front 

slightly arched, slightly notched in the middle, with thickened edge ; the anterolateral edge 

with five sharp teeth (including the orbital angle), of which the two hindei-most are thorn- 

like ; the hinder edge slightly arched ; the orbital gap very narrow, so that the prolongation 

of the basal joint of the antenna is hard to see; the fore edge of the meropodite of the third 

maxilliped only slightly concave, with a small projection at its inner end ; the chelipeds equal, 

without tubercles or thorns except one shai-p thorn at the inner angle of the wrist, the hand 

narrow, with a faint groove above and a groove down each finger, the fingers fis long as the 

upper edge of the palm, gaping, with a few sharpish teeth and hoof-like ends; and the walking 

legs hairy, with spines on the end-joints, and a double end-claw." 

Length : 8 mm. Breadth : 12 mm. (Largest specimen.) Colour in spirit : white ; the 

fingers brown with white tips. 

chelipeds. 

This species differs fi-om most Chlorodopsis in the absence of spines fi:om the back and 


74. ? Chlorodopsis (Cyclodius) ornata Dana, 1852. Alcock, ill. p. 171. 

I have assigned several small specimens to this species, but am uncertain whether they 

are not really the young of Phymodius imgulatus. They agree with Alcock's definition, except


in that the basal joint of the antenna does not fill the orbital gap, though the flagellum is 

not placed at its apex, a small process extending inwards towards the orbit as shown in Dana's 

figure {U. S. Expl. Expd. Crust. Atlas, PI. xii. figs, lie, 11 d). 

Taken on the reef in Male, Goifurfehendu and South Mahlos Atolls. 

Genus Etisodes Dana, 1851. 

75. Etisodes anaglyptus (H. M.-Edw.), 1884. Alcock, iii. p. 133. 

Taken on the reef in Goifurfehendu Atoll and dredged in 3—9 fathoms in Minikoi lagoon. 

76. Etisodes electra (Hbst.), 1801. Alcock, in. p. 133. 

In young specimens the lobes of the front are shorter, and not so equal as in old individuals, 

the middle lobes being distinctly broader than the outer. I doubt the specific distinctness of 

this form from E. anaglypta. 

Taken on reefs and in lagoons in Male, Goifurfehendu, Miladumadulu, Fadifolu and Mini- 

koi Atolls. 

Genus Etisus H. M.-Edw., 1834. 

77. Etisus laevimanus Randall, 1839. Alcock, iii. p. 131. 

Alcock quotes only figures 1 a—b on Dana's plate X., seeming thus to exclude figs. 1 f—h, 

which Dana labels as young females of the same species. My specimen, a female, exactly re- 

sembles these latter figures. 

Taken on the reef at Hulule, Male Atoll. 

Subfamily Eriphiinae. 

Genus Domecia Eyd. and Soul., 1841. 

78. Domecia hispida Eyd. and Soul, 1841 var. ? (Fig. 41 e.) See Alcock, iii. p. 230. 

My specimens agree with the figures and descriptions of B. hispida, but have no hairs on 

the carapace. 

This is a true coral crab, like Trapezia and Melia, and lives among the branches of living 

corals. It was taken on the reef at Goidu, Goifurfehendu Atoll, and seen also in Minikoi. 

Genus Eriphia Latr., 1817. 

79. Eriphia laevimana Latr., 1817. Alcock, iii. p. 214. 

This species, which was taken at Minikoi, lives in holes in the rocks and is rather active 

in its movements. 

80. Eriphia scabricula Dana, 1852. Alcock, III. p. 216. 

Taken on the reef in Minikoi and Addu Atolls. Lives under stones and in coral stocks. 

Subfamily Trapeziinae. 

This group of little, square-bodied crabs, with a broad front and a smooth, usually polished, 

cuticle (Figs. 41 f, 56), is very characteristic of the Indopacific region, to which its members 

G. 34


are restricted, and within which they are everywhere abundant on coral reefs. They find shelter 

on various sessile animals, especially branched corals, from which they are usually not to be 

dislodged except by breaking up the stock, and it is very remarkable that they are found only 

on living corals, and in these only on those branches which are still alive. Yet they do not 

eat or in any way damage their host, contenting themselves with deriving protection from its 

stinging-cells'. In correspondence with this habitat, their legs are rather slender, and have 

end-joints which can be moved through a considerable arc, so as to form with the next joint 

a kind of hook, serviceable for grappling the branches of the host. These end-joints (Figs. 42 B, 

58 c) are remarkable and interesting structures when the habitat of the crabs is borne in 

mind. Besides the peculiar flange working on the joint before, which has been described 

above on p. 242, and is probably an adaptation to clambering, there are several other modi- 

fications, which seem intended to give the animals a better foothold on the rugged and yet 

slimy surface of the coral. Thus the joint is covered with hairs, and among these are a 

number of stout, moveable prickles. The claw at the end of the joint is bent sharply forming 

a hook, and is smooth and pointed in Quadrella, while in Trapezia it is broad and shovel- 

like, and bears above two rows of structures resembling the prickles but rounded at the end. 

It is likely that the smoothness of the bodies of these crabs is due to the same cause as 

that of other semiparasitic Decapods, such as the mussel-prawns and crabs (Pontonia and 

Pinnotheres), and that this cause is the need of inconveniencing as little as possible the 

animals which give them shelter. Trapezia and Tetralia especially affect corals, but Quadrella 

has been taken on Alcyonarians of various kinds, and even among pearl-mussels". 

The Trapeziinae are exceptional among Xanthids on account of their tendency to form 

varieties, and present the feature, unusual in crabs, of definite colour forms. It is possible that 

some of these forms may be physiological phenomena of the same kind as the colour-phases 

of prawns^, but others are associated with structural features, and cannot well be of this nature. 

It is also important to note that, in Trapezia, they bear no relation to the colour of the coral. 

For the present it were well that none of them were overlooked, and I have therefore revived, 

in two cases, colour names which had been dropped, without, however, intending any implica- 

tion as to the nature of the phenomena. 

The synonymy of this group is extremely intricate, and the authority followed here is 

Ortmann, in his late revision [^Zool. Jahrh. Si/st. x. ii. p. 201 (1897)]. 

Genus Trapezia Latr., 1825. 

81. Trapezia ferruginea Latr., 1825 (Fig. 41 F, 42 B). 

i. Var. typica Ortm., 1897, Alcock, ill. p. 220. 

On reefs and in lagoons down to 35 fathoms in Goifurfehendu, Male, Fadifolu, Addu, 

Minikoi, South Nilandu, Suvadiva, and South Male Atolls. 

ii. Var. dentata (Mackay), 1838. Ortmann, loc. cit. p. 204. 

On reefs at Male, Goifurfehendu and Fadifolu Atolls and in Suvadiva lagoon in 25 fathoms. 

' I am much obliged both to Mr Stanley Gardiner and to among the living branches, nor was there any evidence of 

Mr Forster Cooper for information confirnnng tliese .state- damage to the coral caused by them. 

ments. From first to last a very large number of coral - Smith, Proc. ISoston Soc. Nat. Hist. xii. p. 288 (1869). 

stocks were broken up by the members of the expedition, ' Gamble and Keeble, Q. J. M. S. XLtii. Pt. 4. 

and in none of these were Trapezius found anvwhere but

iii. Var. guttata Rlippell, 1830. Alcock, ill. p. 221. 


On the reef in Goifurfehendu and in the lagoons of Mahlos, Suvadiva and North Male 

Atolls down to 25 fathoms. 

iv. Var. muculata (Mackay), 1838. Alcock, in. p. 221. 

On the reefs in Goifurfehendu, Male, Fadifolu and Minikoi Atolls, and in the lagoons 

at Suvadiva and South Nilandu down to 25 fathoms. 

82. Trapezia cymodoce (Hbst.), 1801. Alcock, iii. p. 219. 

The name T. coendea was given by Heller in 1861 to specimens of this species in 

which the blue tinge, found to a greater or less extent in many individuals, was very 

conspicuous. The intermediate cases, however, between pure brown examples and those in 

which blue ijredominates, are so numerous, and form such a complete series, that it is im- 

possible to keep coendea even as a varietal name. 

On reefs and in lagoons down to 35 fathoms in Male, Minikoi, Goifurfehendu, Fadifolu, 

South Nilandu, Suvadiva and Felidu Atolls. 

83. Trapezia digitalis Latr., 1825. Ortmann, loc. cit. 

i. A^'ar. typica = T. digitalis, Alcock, III. p. 222. 

Dark-brown specimens. 


ii. Var. formosa Smith, 1869. {Proc Bost. Soc. N. H. Xil. p. 286.) 

This variety differs so sharply from the dark-brown true digitalis that it seems to deserve 

a separate varietal name. In structure the variety is like digitalis, but it somewhat resembles 

T. J-erruginea in the shape of the front. This feature, however, varies considerably in digitalis. 

The earliest name for the orange-coloured form is formosa Smith. T. corallina Gerstaecker, 

1856, is a coral-red crab. 

lagoon. 

84. Trapezia rufopunctata (Hbst.), 1790. Alcock, iii. p. 222. 

Taken on the reef in Male and Fadifolu Atolls, and in 19 fathoms in South Nilandu 

Genus Tetralia Dana, 1851. 

85. Tetralia glaberrima (Hbst.), 1790. Alcock, iii. p. 223. 

The black colouring on the front of this species varies in breadth from an almost 

imperceptible line, through bands of greater breadth, to a suffusion of the whole carapace 

and limbs with dark coloration, and no purpose would be served by keeping Dana's name 

nigrifrons. But the colouring of the legs will, I think, be found to fall into definite varieties. 

The walking legs, in short, may be either: (1) Uniformly yellow. (2) Uniformly dark brown. 

(3) Yellow banded with dark brown across the middle of each joint. (4) Yellow with a sharp 

black spot at the end of the meropodites and propodites. (5) Yellow with narrow brown 

longitudinal strijjes. 

An examination of a long sei-ies of specimens would jjrobably give interesting results. 

Taken on reefs and in lagoons down to 35 fathoms in Goifurfehendu, Fadifolu, Male, 

Felidu, and Minikoi Atolls. 

34—2


Genus Quadrella Dana, 1851. 

86. Quadrella coronata Dana, 1852. Var. granulosa n. See Alcock, iii. p. 266. 

All the specimens of Quadrella coronata in the collection belong to a new variety, which 

differs from the type in the following features: (1) The carapace is distinctly broader than 

long. (2) The chelipeds are only about 2i times as long as the carapace. (3) The chelipeds 

are frosted over with tiny granules set in short rows athwart the limb. On the underside 

of the hand the granules are less regular in arrangement, and, projecting in profile, give 

the inner (lower) edge of the hand an in-egular, fine denticulation. (4) The colour in spirit is 

a uniform pale flesh-colour, purplish in places. 

By the first three of these features the new variety is allied to var. maculosa Ale, but 

it differs from that variety in the following points : (1) The fore edge of the arm is not 

serrate, but bears about ten long thorns. (2) The coloration in spirit is different. 

The following key shows the jDrincipal characters which separate the known varieties of 

Q. coronata: 

I. Carapace as long as broad. Chelipeds polished. Colour in spirit uniform milk-white. 

[Fore edge of arm spined. Chelipeds 2f times the length of the carapace.] 

Var. A, type Dana, 1851. 

II. Carapace broader than long. Chelipeds more or less frosted over with granules. 

More or less colour on the body. 

A. Fore edge of arm spined. Colour in spirit uniform pale flesh-colour. [Chelipeds 

2^ times the length of the carapace.] 

Var. B, granulosa n. 

B. Fore edge of arm serrate or finely denticulate. Colour arranged in a pattern. 

i. Fore edge of arm serrate. Chelipeds 2^ times the length of the carapace. 

Colour in a network of fine lines. 

Var. C, reticulata Ale, 1898. 

ii. Fore edge of arm finely denticulate. Chelipeds 2f times the length of the 

carapace (?). Colour in tiny purple dots. 

Var. D, maculata Ale, 1898. 

Var. granulosa was taken on a Gorgonacean dredged in 39 fathoms in Suvadiva Atoll 

and on a red Alcyonarian dredged in 25 ftithoms in the same Atoll, and was dredged in 

23 fathoms in Mahlos Atoll. 

87. Quadrella bispinosa, n. sp. (Fig. 58.) 

Diagnosis : " A Quadrella which is near akin to Q. coronata but differs fi'om it in the 

following points: (1) The carapace is distinctly broader than long. (2) There is a spine on 

the anterolateral edge of the carapace, rather farther from the spine at the outer angle of


the orbit than from that which marks the junction of the antero- and postero-lateral edges, 

and rather smaller than the latter spine. (3) The upper, inner angle of the orbit is not 

spiniform, but is somewhat raised. 

The minute teeth which edge both 

the upper and lower rims of the 

orbit are, on this angle, increased 

in size and set farther apart, so 

that one or two of them can just 

be seen with the naked eye. 

(4) The chelipeds are frosted over 

with tiny granules as in some 

varieties of Q. coronata. The 

granules are somewhat larger 

underneath the hand. (.5) The 

arm is rather shorter than in Q. 

coronata. (6) There are few thorns 

on the end-joints of the legs, but 

these joints are very hairy. (7) The 

colour in spirit is a rich orange- 

brown, paler on the walking legs 

and fingers. 

A female with eggs was 

dredged in 25 fathoms in Addu 

Atoll. 

Fig. 58. Quadrella hispiiwsa; a. whole animal, b. part of outside of hand 

enlarged to show the scales, c. end of walking leg enlarged. 

Subfamily Oziinae. 

It is somewhat remarkable that the collection contains no example of this subfamily, 

whose genera {Ozius, Epixanthus, Euruppellia and Baptozius) contain several very common 

species which have been recorded from surrounding localities such as India, Ceylon, the Red 

Sea, and the Seychelles. Both Alcock (foe. cit.) and Ortmann {Zool. Jahvh. Syst. Vil.) oc- 

casionally report species from the Maldives or Laccadives, but neither of them mentions a 

member of the Oziinae from those islands. 

Genera incertae sedis. 

Genus Gaecopilumnus, n. 

Among the decapods taken on the reef at Naifaro in Fadifolu Atoll is a small, Pilumnus- 

like crab whose orbital region has undergone a remarkable transformation, so that the animal 

appears to be absolutely blind. In a few words, this transformation consists in the orbits 

becoming very small, almost on the underside of the carapace, and completely filled by 

the eyestalks, while the small cornea lies on the underside of the stalk and is hidden in 

the orbit, so that the outline of the body is quite unbroken over the area where the open 

orbit should lie. 

I propose to establish for this crab a new genus, under the name of Gaecopilumnus, 

with the following characters: (1) Carapace roughly square, convex both fore and aft and from


side to side, hairy, and granular. (2) Front narrow, triangular with rounded apex, hollowed 

and grooved above. Front-orbital breadth small. (3) Anterolateral edge in-egularly set with 

small spines, passing evenly into posterolateral, without orbital angle. (4) Orbits small, com- 

pletely filled by eyestalks, not closed. (5) Eyes with relatively large end-joint but small cornea, 

which is on the underside at the free end. The upper side is granular and hairy like the 

carapace, but the underside is smooth and its cuticle transparent. (6) Antennae with rather 

Fig. 59. Caecopilumnus hirsutus ; a. whole animal, b. outside of hand, c. view of underside with roof of mouth laid 

bare, d. front view to show orbits closed by eyestalks, e. underside of eye enlarged, showing small cornea and 

mass of pigment within stalk. The hairs have been taken off the right side of the body. 

broad basal joints, which do not completely fill the orbital gap. (7) Thir-d maxillipeds \vith 

broad, squarish ischiopodite and meropodite, the latter having its fore edge rounded, and 

narrow exopodite. The caqjopodite is attached distally to the meropodite. (8) Endostome 

ridges present and distinct, but not reaching the fore edge of the mouth. (9) Chelipeds equal, 

granular, with pointed fingers. (10) Walking legs stout and of moderate length. 

The single specimen being a female, it is impossible to describe the characters of the male. 

As to the habits, nothing is known, save that the crab was taken on the reef There is 

nothing in its appearance to suggest a parasitic existence except the reduction of its eyes. 

Probably the peculiar conformation of the orbits is due to some circumstance which makes it


necessary to guard against the entrance of foreign bodies or enemies. Whether the eyestalks 

can be raised, upon occasion, so that the small eyes are exposed, it is impossible to say, but 

in the spirit specimen they are certainly so firmly fixed that they cannot be moved without 

breaking the carapace. The specimen is not well enough preserved to allow of statements being 

made as to the retina, but a small mass of pigment can be seen through the transparent 

underside of the eyestalk, at some distance from the cornea. 

The systematic position of the genus is doubtful, especially in view of the fact that 

the male is not known. If it belong to the Xanthidae, it is perhaps more closely related 

to the Menippinae than to any other subfamily, but it may quite possibly be a Catometope 

allied to the Rhizopinae, and especially to the species which Miers referred doubtfully to 

Typhlocarcinus under the name T. integrifrons \Âiin. Mag. N. H. (.5), VIII. p. 260 (1881)]. 

1. Caecopilumnus hirsutus, n. sp. (Fig. 59). 

Diagnosis: "A Caecopilumnus with the carapace moderately convex from side to side, 

strongly so fore and aft, granular and pubescent all over, the front strongly bent downwards, 

its sides sloping inwards to a groove in the middle, fringed with long hairs, which are also 

found all over the orbital region and eyestalks and along the sides of the carapace ; the 

orbit very small, without orbital tooth or spine or notches in the rim ; the anterolateral edge 

passing with an even sweep into the posterolateral behind, and in front fading away at a 

point behind and above the outer angle of the orbit, which thus comes to lie to a great 

extent on the underside of the body; the granules of the carapace enlarged along the 

anterolateral edge into small spines, arranged in four irregular sets ; the hinder edge hollowed 

the regions rather faintly marked ; 

the eyestalks large relative to the orbits, which they 

entirely fill, fitting close against the thin, non-prominent rims, and thus complete the outline 

of the carapace, simulating the carapace in their granulation and hairs ; cornea small and 

hidden on the underside of the eyestalk ; chelipeds equal, granular, pubescent and hairy, these 

features extending to the fingers, the fingers compressed and grooved, with interlocking teeth 

on their apposed edges, and sharp, crossing tips ; and 

walking legs of moderate length, very 

stout, especially the second and third, which have very long propodites, covered with long 

hairs but without spines." 


Genus Maldivia. 

A white Gorgonacean, dredged in eight fathoms of water, in North Male, bore a minute 

but very interesting symbiotic crab, whose peculiarities justify the setting up of a new genus 

for it. The following are the characters of this genus : 

(1) Carapace hexagonal, swollen, a 

little longer than broad, hairless, roughened with granulations which pass into spines at the 

sides, and with indications of the regions. (2) Front broad, triangular, widely grooved, bent 

strongly downwards. (3) Anterolateral edge toothed, about equal to posterolateral. Hind edge 

wavy. (4) Orbits large, very slanting, not fully closed. (5) Abdomen of male seven-jointed. 

(6) Endostome ridges present, but not very strong. (7) Eyes large. (8) Antennae with slender 

basal joints which do not touch the fi-ont, and long flagella. (9) Merus of third inaxilliped 

about as long as broad, without a notch in the fore edge, which is straight. (10) Chelipeds 

stout, Piluvinus-Yike, fingers not hollowed at the tip. (11) Walking legs moderately stout. 

The genus resembles Pilumnus in the shape of the hands and the endostomial ridges. 

;


The form of the carapace, the presence of endostomial ridges and the symbiotic habits 

recall Quadrella. The front and 

the spinate region at the side of 

the granulated carapace, and again 

the endostomial ridges, show a cer- 

tain resemblance to Caecopilunmus 

described above, though the eyes 

and orbits are very different. The 

form of the antennae points to its 

true position being among the Me- 

nippinae, perhaps in the neighbour- 

hood of Pilumnus. 

(Fig. 60). 

2. Maldivia symbiotica, n. sp. 

Diagnosis : 

" A Maldivia whose 

carapace is roughened with small 

tubercles, which in places, as on 

the anterolateral edge, pass into 

spines; the latter edge with four 

lobes, including the orbital lobe, 

each lobe bearing several spines, of 

which one is larger than the rest, 

while the lobes decrease in size from behind forwards; the chelipeds equal, bearing on the 

outside spines set in rows, a row along the upper edge being specially long, the fingers shorter 

than the hand; the walking legs moderately stout, bearing some long hairs." 

Length : 1-5 mm. Breadth : 

1. Kraussia rugulosa (Krauss), 1843. 

IQ 

Fig. 60. Maldivia symhiotica, found on a gorgonian, whole animal 

greatly enlarged. 

mm. Colour in spirit : white. 

Family Atelecyclidae. 

Subfamily Thiinae. 

Genus Kraussia Dana, 1852. 

Kraussia rugulosa, Dana, U.S. Expl. Expd. Crust, p. 302, pi. 19, fig. 1 (1852). 

Taken on the reef in Male, Goifurfehendu and Minikoi Atolls. 

2. Kraussia integra (de Haan), 1837. Alcock, I v. p. 97. 

A small specimen from Mahlos Atoll shows characters which recall K. nitida Stimps., 

1858, in that the frontal lobes are subdivided, though not so deeply as in Stimpson's species, 

and the carajjace is somewhat narrower than in adult specimens of K. integra. The teeth 

on the dactylopodites of the legs are small. 

Taken on the reef in Male and dredged in 24 fathoms in Mahlos Atoll.

MAEINE CRUSTACEANS. 271 

Family Hapalocarcinidae. 

This interesting little family of symbiotic crabs, of which, in one case, only the females 

are known, is, as Caiman has shown [TV. Linn. Soc. Zool. (2), viii. p. 43 (1900)], quite incertae 

sedis, and is taken here for convenience alone, and not on account of any relationship to the 

Xanthidae. It is discussed at length in Caiman's paper. For some remarks on the import- 

ance of these crabs as affording by their holes a foothold for destructive boring organisms 

in the coral blocks, see a paper by Mr Stanley Gardiner in this part of the present 

publication. 

Genus Hapalocarcinus Stimps., 1857. 

1. Hapalocarcimos marsupialis Stimps., 1857. Caiman, loc. cit. 

Galls containing specimens of this crab were found on Pocillopora in the lagoon at 

Minikoi and on the reef at Hulule, Male Atoll. 

2. Gryptochirus coralliodytes Heller, 1861. 

Genus Gryptoclm-us Heller, 1861. 

Cryptochirus coralliodytes, Heller, S. B. Ak. Wins. Wien, XLiii. i. p. 366, pi. II. figs. 33—39 

(1861); Semper, Anirnal Life, London, 1881, pp. 217, 221—223; Caiman, loc. cit. p. 47. 

Mr Stanley Gardiner has kindly given me the following note on this species : " A block 

of Leptoria tenuis which had a large number of round holes on the surface, up to 4 mm. 

across, was broken up. The holes, when traced in, were nearly all found to be occupied 

by a symbiotic crab [Cryptochirus]. In two holes, however, were crabs of the ordinary form 

[Pseudozius, see above, p. 241]. The holes varied in depth from 1—30 mm., the coral itself 

being in the latter position 48 mm. thick. Normally the animal would appear to live close 

to the surface—some slightly projected, with the carapace as a kind of shield closing the 

hole. When the block becomes more or less dry, they retreat into the bottom of the holes. 

I found some deserted holes, perhaps due to an accident in breaking the coral, but the crabs 

certainly could not wander, on account of the small size of the entrances of the holes. It 

is obvious that the crab must have taken up its abode on the coral, which afterwards 

enclosed it. [This refers to the inner hole, not to the funnel round it.] These commensals 

are extremely common in Leptoria from the lagoon at Minikoi, but are never found in 

specimens from the outer reef They are rare on other corals, occasionally occurring in 

massive astraeids from the lagoon at Minikoi, but not apparently in branching corals, fungoids, 

or perforate corals." 

35

ON THE FISHES FEOM THE MALDIVE ISLANDS. 

I. DREDGED. II. FRESH-WATER. 

By C. TATE REGAN, B.A., Assistant at the Natural History Museum, 

S. Kensingto7i. 

The Collection of Fishes from the Maldive Islands has been divided into two series. The 

first consists of the specimens dredged or trawled within the lagoons of the atolls. The second 

contains a few specimens taken from fresh-water pools on some of the islands. 

The use of formalin as a preservative has rendered the fin rays very brittle, so that in 

most of the specimens the fins are more or less damaged. 

I take this opportunity of gratefully acknowledging my indebtedness to Mr Boulenger, who 

has very kindly looked through the collection under notice, and confirmed my identifications. 

I. DREDGED FISHES FROM WITHIN THE LAGOONS. 

There are 321 specimens, belonging to 65 species. They are mostly small, the lagoons 

probably being nurseries for young fish. This has made identification a very difficult matter 

in many cases, so that some specimens have been referred only to their genus, and many, 

which seem without doubt to belong to hitherto undescribed species, have been only briefly 

described, and have not been given specific names. 

A list of the species follows. For convenience of reference I have kept to the arrangement 

of families in Giinther's Study of Fishes. 

ACANTHOPTERYGII. 

Fam. Percidae. 

1. Apogon auritus, C. and V. Suvadiva, 44/". (fathoms). 

2. Apogon elliotti, Day. {Apogon nigripinnis, Gthr. (Part) ; Apogon arafurae, Gthr.) 

Gunther identified specimens belonging to this species with Apogon nigripinnis, C. and V., 

and later described a somewhat large specimen from the Challenger Collection as a new species.

ON THE FISHES FROM THE MALDIVE ISLANDS. 273 

Apogon arafurae^ : Day distinguishes between this species and Apogon nigripinnis, C. and V., 

from which it differs in many important characters. 

In the specimens in the British Museum Collection, and in those from the Maldives, the 

length of the snout is | to | of the diameter of the eye, and in the Challenger specimen, 

described as Apogon arafurae, the eye diameter is equal to the length of the snout, which 

is contained 4 times in the length of the head, this being due to the fact that the eyes 

become relatively smaller in larger fish. Day's statement that the length of the snout is ^ 

the diameter of the eye is probably, therefore, inaccurate. 

Suvadiva, 44/, and Mulaku, 27/ 

3. Apogon nigripinnis, C. and V. Haddumati, 40/ 

A male fish, 47 mm. in total length, had its mouth full of eggs ; and a specimen in the 

British Museum Collection shows the same phenomenon, which is, no doubt, a case of protec- 

tion by the parent. 

4. Apogon septemstriatus, Gthr. S. Nilandu, 36 and 30/ 

5. Apogon fasciatus, White. S. Nilandu, 30/ 

6. Apogon sp. N. Male, 35/ 

D. VII, 19 ; A. II, 8 

; L. lat. about 25. 

This species is represented by two very small specimens, each 15 mm. in total length. 

The head is nearly half the total length. The body is dark brown, with a black band at 

the base of the dorsal, and a broad black longitudinal band ventrally. They cannot with 

certainty be said to belong to a hitherto undescribed species. 

7. Anthias cooperi, n. sp. 

D. X, 16; A. Ill, 7; Sc. 52, J'-^; L. lat. 50. 

Depth of body three times in total length, length of head 3J times. Snout scaly, shorter 

than the eye, the diameter of which is slightly greater than the interorbital width, and is 

contained three times in the length of the head. Lower jaw slightly projecting, scaly. Maxil- 

lary scaly, extending to below the centre of the eye, the width of its extremity | the diameter 

of the eye. Two or three spines at the angle of the preopercle ; sub- and interopercle serrated 

two opercular spines. Dorsal spines increasing in length to the fourth, rest subequal ; no notch 

between spinous and soft portions ; base scaly. Ventrals a little longer than the pectorals, not 

quite so long as the head. Anal spines strong, the first shortest, the second longer than the 

third ; soft portion scaly at the base, pointed, the third ray longest. Caudal moderately emarginate. 

Caudal peduncle as long as deep. Lateral line curved. Coloration uniform, in spirit. 

This species is allied to Anthias cichlops, sqiiamipinnis and townsendi, from all of which 

it differs in having more numerous scales, and in having spines at the angle of the preopercle 

in this latter feature it resembles Anthias formosxis and rnargaritaceus, from which it differs 

in the important character of having the lateral line curved, not forming an angle below the 

hinder dorsal rays. Length of the specimen, 47 mm. 

Haddumati, 40/ 

' Day, Fishes of India, i. pp. CO and 63. 

35—2 

;

274 C. TATE REGAN. 

8. Epinephelus sex/asciatus, C. and V. 

Three specimens less than 30 mm. in total length have a prominent spine at the angle 

of the preopercle, equal in length to ^ the diameter of the eye. A somewhat larger specimen, 

48 mm. long, has the normal adult arrangement. 

Haddumati, 35/ 

Fam. MuUidae. 

9. Upenoides tragvla, Richardson. Mulaku, 27/. 

Fam. Cirrhitidae. 

10. Cirrhitichthys oxycephalus, Blkr. Haddumati, 40 / 

Fam. Scorpaenidae. 

11. Cocotropus roseus, Day. N. Male, 35 /. 

12. Minous mmiodactylus, Bl. Schn. S. Nilandu, 36 /. N. Male, 35 /. 

13. Pelor didactylum, Pall. Suvadiva, 30 / 

14. Amhlyapistus macracanthns, Blkr. Suvadiva, 30/. 

15. Pterois zebra, C. and V. Haddumati, 35 /., and Kolumadulu, 35 / 

Fam. Acanthuridae. 

16. Naseus {1 Keris) sp. Suvadiva, 37/ 

D. VI, 29; A. ii, 30. 

A single specimen, 37 mm. in total length, closely resembles Keris amhoinensis, Blkr., 

but differs in having the first dorsal spine longer than the others. Probably, like Keris am- 

hoinensis. it is the young form of a species of Naseus. 

Fam. Trachinidae. 

17. Percis punctulata, C. and V. N. Male, 35 / 

18. Ghanipsodun vorax, Gthr. Suvadiva, 30 /, and Mulaku, 27 / 

19. Percophis sp. 

D. VII or VIII, 30—35 ; A. 30—35 ; 

Sc. 52. 

A single badly preserved specimen, 35 mm. in total length, undoubtedly belongs to this 

genus, which has not before been known to occur in the Indian Ocean, only one species, 

Percophis hrasilianus, from the coast of Brazil, having been described. 

Depth of body 12 times in the total length, length of head four times. A longitudinal 

band along the middle of the side. The shape and proportions of the body are exactly the 

same as in Percophis brasilianus, which has, however, much smaller scales. 

Kolumadulu, 33 /


Fam. Pediculati. 

20. Antennanus nummifer, Cuv. Haddumati, 35 f. 

Fam. Cottidae. 

21. Platycephalus asper, C. and V. Mulaku, 27 /., and N. Male, 35 /. 

22. Platycephalus tuberculatus, C. and V. Koluraadulu, 35 /., and Haddumati, 40 /. 

23. Platycephlus spinosus, Schleg. Kolumadulu, 35 /. 

In this specimen, as in that in the British Museum Collection, the number of scales in 

a longitudinal series is 33, not 40 as given by Schlegel. 

24. Platycephalus svbfasciatus, Gthr. Mulaku, 27 /. 

Fam. Cataphracti. 

25. Pegasus draconis, Linn. Haddumati, 40 /'. 

Fam. Gobiidae. 

26. Gobius caninoides, Blkr. Mulaku, 27 /. 

27. Gobius ornatus, Rupp. S. Nilandu, 36 and 30 /., Felidu, 34 /., Mulaku, 27 /., and 

Kolumadulu, 33 / 

28. Gobius semidoliatus, C. and V. N. Male, 35 / 

29. Gobius ophthalmotaenia, Blkr. S. Nilandu, 36 /., and N. Male, 35 /. 

30. Periophthalmus sp. S. Nilandu, 35 /. 

One specimen, 33 mm. long. The ventral fins are not united. Probably a young specimen 

of Periophthalmus chrysospilos. 

31. Callionymus longicaudatus, Schleg. S. Nilandu, 36 and 30 f. 

32. Callionymus lunatus, Schleg. Suvadiva, 44 f., and Haddumati, 40 f. 

33. Callionymus sp. Suvadiva, 37 /. 

D. IV, 7 ; A. 6. Length of the head about three times in the total length. Gill opening 

small, superior. Preopercular spine with four posterior teeth. Eye diameter about three times 

in the length of the head. Brownish, with darker bands or blotches, and with a series of 

narrow transverse bands on the gill membranes. The single sjêcimen is 24 mm. in total 

length, and probably belongs to a hitherto undescribed species. 

34. Petroscirtes sp. 

D. 26 ; 

Fam. Blenniidae. 

A. 16. This fish was dredged at Bemamfuri, N. Mahlos, in the lagoonlet, at a 

depth of four fathoms, in a Gastropod shell. Mr Gardiner says, "I kept this fish alive for 

some hours in a basin, it would swim round, always returning to its house. The favourite 

position was with the head just projecting out of the mouth of the shell." 

The specimen is 28 mm. long.


35. Clinns sp. Haddumati, 40 /. 

D. 24; A. 16; V. i, 3; Sc. 30, 11. 

The depth of the body is equal to the length of the head and is contained 3| times in 

the total length. Snout shorter than the eye, the diameter of which is twice the interorbital 

width, and is contained 3| times in the length of the head. The single specimen is 30 mm. 

in total length, and probably belongs to a species not before described, and differing from 

nearly all other species of Clinus in the large size of the scales. 

ACANTHOPTERYGII PHARYNGOGNATHI. 

Fam. Pomacentridae. 

36. Dascyllus melanurus, Blkr. Felidu, 34 f. 

37. Amphiprion sebae, Blkr. S. Nilandu, 30 /., and N. Male, 35 /. 

38. Pomacentrus pimctatus, Quoy and Gaim. Suvadiva, 43 /., and Haddumati, 40 /. 

Fam. Labridae. 

39. Labroides dimidiatus, C. and V. Felidu, 34 /. 

40. Julis schwanefeldii, Blkr. Mulaku, 27 /. 

41. Cheilinus sp. Mulaku, 27 /. 

Four specimens 28—45 mm. long may be young specimens of Cheilinus calophthalmus. 

42. Cheilinus sp. Mulaku, 27 /, and N. Male, 35 / 

Several young specimens less than 30 mm. long may belong to Cheilinus ceramensis. 

43. Cheilinus sp. Suvadiva, 43 /. 

Two very small specimens may belong to Cheilinus celebicus. 

ANACANTHINI. 

Fam. Pleuronectidae. 

44. Rhomboidichthys grandisquamis, Schleg. 

Describing this species', Schlegel says, " The pectorals are not elongated. The males have 

a spine on the maxilla and another on the anterior margin of the lower eye. The interorbital 

width is equal to the diameter of the eye in the males, and is half the diameter of the eye 

in females. The body is more elongated in the females." 

With regard to these features in the specimens from the Maldives : The 

pectorals are 

elongated in some, and not in others, without relation to size or sex. All the males have a 

maxillary spine, but some are withovit an antorbital spine. The females have neither spine. 

The interorbital width varies from f to 1^ diameters of the eye in males, and j to ^ diameter 

in females, and, as a rule, the eyes are relatively further apart in the larger specimens. The 

greatest depth of the body is not more in males than in females, but the eyes being wider 

' Schleg., Fauna Japonica, Poiss., p. 183.


apai't in the former, the head and anterior part of the body is broader, so that the females 

appear more elongated. 

This species is distinguished from Rhornhoidichthys poecilurus, Blkr., by the absence of a 

pair of black spots on the caudal, and by the greater size of the maxilla, which is contained 

2| times in the length of the head. 

Suvadiva, 44 /, S. Nilandu, 36 and 30 /, Felidu, 34 /., and Mulaku, 27 /. 

45. Rhomboidichthys poecilurus, Blkr. {Rhornhoidichthys grandisquama, Gthr. ; and Rhorn- 

hoidichthys spilurus, Gthr.) 

Bleaker, describing this species, gives the number of scales in a longitudinal series as 

about 45. Gllnther distinguishes between two species, Rhomboidichthys grandisquama, with 40 

scales in a longitudinal series, which he identifies with Rhomhus grandisquama, Schleg., in 

reality a quite distinct species; and Rhornhoidichthys spilurus, with 48 scales in a longitudinal 

series, and the eyes closer together. 

In the 13 specimens from the Maldives the scales vary from 40—48 in a longitudinal 

series, nearly all intermediate numbers being found. The males have a knob on the maxilla, 

and the interorbital width equal to the diameter of the eye. The females have no maxillary 

knob, and the interorbital wdth is about i the diameter of the eye. In immature fish the 

eyes are closer together. 

This species is distinguished from Rhornhoidichthys grandisquamis in that it has a pair 

of black spots on the caudal, in the middle of the upper and lower margins respectively, and 

has a smaller mouth, the length of the maxilla being contained 3|^ times in the length of the 

head. 

Suvadiva, 44 /, and 34 /. 

46. Rhomboidichthys intermedius, Blkr. Suvadiva, 44 /., and Felidu, 34 /. 

47. Rhomboidichthys pantherinus, Blkr. Suvadiva, 43 /, and S. Nilandu, 36 and 30 /. 

48. Brachypleura xanthosticta, Gthr. Suvadiva, 44 f., and Mulaku, 27 /. 

49. Cynoglossus hrachycephalus, Blkr. Mulaku, 27 /. 

50. Saviaris macvlatus, Gthr. Suvadiva, 45 f. 

In the Challenger Report this species is described, from one specimen, as having three 

series of dark spots, five along the dorsal profile, four along the latei-al line, and five along 

the ventral profile. In two small specimens from the Maldives, each 29 mm. in total length, 

these spots are connected by dark lines, the colour being preserved better. 

Samans cristatus. Gray, differs from Samaris maculatus in having a somewhat smaller 

head and deeper body, and in the elongation of the anterior dorsal rays, but the two 

specimens in the British Museum Collection have dark spots feebly visible in the same 

position as in Sa7na7-is maculatus. These specimens are males, and that named Samaris 

maculatus is a female, and apparently the small specimens from the Maldives are females, 

so that it seems possible that the differences are not specific, but sexual. The elongation 

of the anterior dorsal rays is characteristic of the males in the allied genus Brachypleura, 

and in many other fishes of this family.


In Samaris maculatus the length of the head is 4 times in the total length, the depth 

of the body 2| to 3 times. 

In Samaris cristatus the length of the head is 4i—5 times in the total length, the 

depth of the body 2|- times. 

51. Solea poropterus, Blkr. Mulaku, 27/. 

PHYSOSTOMI. 

Fam. Scopelidae. 

52. Saurus varius, Lacep. S. Nilandu, 36/. and 30/, Felidu, 34/, Kolumadulu, 33/, 

and N. Male, 35/ 

53. Saurida nebidosa, C. and V. S. Nilandu, 36/, Felidu, 34/, and N. Male, 35/ 

54. Saurida tumbil, Bl. Suvadiva, 44/, Felidu, 34/, and Kolumadulu, 33/ 

55. Syngnathus sp. Haddumati, 35/. 

LOPHOBRANCHII. 

Fam. Syngnathidae. 

D. 23. Osseous rings 15— 16 + 35—40. Length of the head 8 times in the total length. 

Snout a little shorter than the rest of the head. A bony ridge crosses the opercle. Edges 

of osseous rings serrated. Dorsal fin commences behind the anus. Brown vertical bands on 

the body. 

Two specimens, each 55 mm. long. 

56. Ichthyocainpus belcheri, Kaup. Suvadiva, 44/ 

Fam. Solenostomidae. 

57. Solenostoma paradoxmn, Pall. Mulaku, 27/ 

Bleeker has described small specimens of a species of Solenostoma with a slender snout, 

in which the caudal peduncle is longer than the base of the second dorsal, and named them 

Solenostoma brachyuruni. One of these is in the British Museum Collection. Giinther has 

written in the Museum Catalogue, " Considering that we know nothing of the changes which 

Solenostoma undergoes during its growth, it is to be regretted that Dr Bleeker did not 

examine these specimens more carefully, but merely attached a new name to them." 

The specimen from the Maldives seems undoubtedly of the species Solenostoma paradoxum. 

The snout is more slender and the caudal peduncle relatively longer than in the adult. 

Probably the badly preserved sjaecimen labelled Solenostoma brachyarum in the British Museum 

Collection also belongs to this species, in which case the changes during growth can be 

shown thus 

: 

Depth of Suout Leugtb of Caudal Peduncle 

Total Length Length of Snout Base of Second Dorsal 

(Specimen in Brit. Mus.) 50 mm. \ ^ 

(Maldive specimen) 67 mm. \ ^ 

(Specimen in Brit. Mus.) 97 mm. ^ |


PLECTOGNATHI. 

Fam. Sclerodermi. 

58. Balistes niger, Mungo Park. Haddumati, 40/ 

59. Monacanthvs nasicornis, Schleg. Suvadiva, 37/ 

60. Monacanthus oculatus, Gthr. S. Nilandu, 30/. 

61. Monacanthus choirocephalus, Blkr. Suvadiva, 43/, and Mulaku, 27/ 

62. Monacanthus sp. Suvadiva, 45/ 

D. 24; A. 24. Dorsal spine barbed. Ventral spine moveable. The specimen is too small 

for determination of the species. 

63. Ostracion cornutus, Linn. N. Male, 35/ 

The specimen is 24 mm. long, and differs from the adult in having a well-developed 

spine on the back, in the lesser development of the antorbital and ventral spines, and in 

having a more projecting snout. A similar specimen in the British Museum Collection is 

labelled Ostracion cornutus. 

64. Tetrodon sp. S. Nilandu, 36/ 

Fam. Gymnodontes. 

D. 8 or 9; A. 6 or 7. The back is broad, snout equal in length to the diameter of the 

eye and also to the interorbital width. A simple perforate nasal tentacle on each side. Body 

covered with three-rooted spines, except on the tail. Purplish brown above, lighter beneath 

small brown spots on the back. The single small specimen almost certainly belongs to a 

hitherto undescribed species. 

65. Tetrodon valentini, Blkr. Haddumati, 40/ 

II. FISHES TAKEN IN FRESH-WATER POOLS. 

There are 14 specimens belonging to 6 species, two of which have not been described 

before. They are mostly marine fishes which are known to ascend estuaries into fresh-water, 

or are allied to fishes with this habit, only one being a true fresh-water fish. A list of 

the species follows. 

1. Gerres maldivensis, n. sp. 

D. IX. 10, A. III. 8 ; Sc. 40^^^. 

ACANTHOPTERYGII. 

Fam. Percidae. 

Depth of body 2^ times in the total length, length of head 2f times. The length of 

the snout is equal to the interorbital width and f the diameter of the eye, which is con- 

tained 2| times in the length of the head. The maxilla extends to below the first third 

G. 

- 

36 

;


of the eye. The caudal peduncle is nearly as high as long. The second dorsal spine is 

the longest, and is | the length of the head ; from it they decrease in length to the fifth, 

the rest subequal. The second anal spine is longer than the third. Pectorals f the length of 

the head. Ventrals do not quite reach the anal. Caudal deeply forked. Light, with indistinct 

dark vertical streaks. Length of specimen, 73 mm. 

Fishes of this genus commonly ascend estuaries into fresh water. A fresh-water pool, 

surrounded by mangroves, in the centre of Landu, Miladumadulu Atoll. 

2. Gohius criniger, C. and V. 

Fam. Gobiidae. 

From the lake, Kendikolu, Miladumadulu Atoll. 

Fishes of this species are common in backwaters. 

3. Miigil coeruleomaculatus, Lacep. 

Fam. Mugilidae. 

Fishes of this genus commonly ascend tidal rivers, and a few, but not those of this 

species, are entirely fresh-water. 

From the mangrove lake, Landu, Miladumadulu Atoll. 

4. Barbiis vittatus, Day. 

PHYSOSTOMI. 

Fam. Cyprinidae. 

A true fresh-water fish, from the bathing pool, Hulule, Male Atoll, and from the man- 

grove lake, Landu, Miladumadulu Atoll. 

5. Chanos salmoneus, Bl. Schn. 

Fam. Clupeidae. 

Fish of this species ascend rivers, and have been introduced and thrive in fresh-water 

tanks in India. From the lake, Kendikolu, Miladumadulu Atoll. 

6. Chanos gardineri, n. sp. 

D. 14, A. 9; P. 16, V. 11; Sc. 70—75ii. 

Depth of body 4f times in the total length, length of head 3J times. Snout shorter 

than the eye, the diameter of which is equal to the interorbital width, and is contained 

31 times in the length of the head. The scales are enlarged on the back just behind the 

head, and on the abdomen. Dorsal highest in front, the longest ray | the length of the head, 

margin concave, two rows of scales at the base. Pectorals rounded, more than ^ the length of 

the head. Ventrals rounded, arising beneath the posterior ^ of the base of the dorsal. Anal 

scaly at the base, margin concave. Caudal deeply forked, its longest ray equal to the length 

of the head. Caudal peduncle twice as long as high. 

The colour is probably similar to that of Chanos salmoneus, but owing to preservation 

of the specimens in formalin this cannot be certainly stated.


The head is much larger, and the body shorter, not so deep, and less compressed than 

in Chanos salmoneus. The scales are less numerous, and the pectorals and ventrals rounded, 

not pointed. Of all the supposed species of Chanos which have been described under various 

names, and are now generally regarded as varieties of Chanos salmoneus, none are found to 

correspond with this species. Whenever proportional measurements are given the length of the 

head is described as | of the total length without the caudal, or as 5^ times in the total 

length with the caudal. The depth of the body is never less than 5^ times in the total length, 

with the caudal. The pectorals are always described as pointed. In some cases the scales 

are given as less than 80 in a longitudinal series, i.e. in Chanos pala, Cantor, and Chanos 

orientalis, Blkr., but this is the only point of agreement. Sometimes no characters of specific 

importance are given, e.g. Leuciscus zeylonicus, Bennett. 

The conclusion is that this species is very distinct, and has not been described befoi-e. 

There are three specimens, 116, 104, and 74 mm. in total length, from the north pool 

of Hulule island, Male Atoll. 

36—2

THE MARINE TURBELLARIA, 

WITH AN ACCOUNT OF THE ANATOMY OF SOME OF THE SPECIES. 

By Frank Fortescue Laidlaw, B.A. (Cantab.), Demonstrator and Lecturer 

in the Owens College, Manchester. 

(With Plates XIV. and XV. and Text-Figiires 61—73.) 

CONTENTS. 

PAGE 

I. Systematic List, with Notes on the Anatomy of the Species ..... 282 

Planoceridae—Leptoplanidae—Cestoplanidae — Pericelidae, nov. fam. —Pseudoceridae 

Prosthiostomidae. 

II. Notes and Conclusions 303 

Planocera and a new Genus 

— 

Thysanozoon and Thyaanoplana—Distribution in the 

Indian Ocean—Parasites—Gut Diverticula—Relationships of the Cotylea—Co- 

tylea and Acotylea—Origin of Nuchal Tentacles—Natural History Notes. 

III. Literature 310 

I. SYSTEMATIC LIST, WITH NOTES ON THE ANATOMY OF THE SPECIES. 

ACOTYLEA. I. Family Planoceridae. 

1. Planocera armata, sp. n. (PL XV. figs. 10, 11, and 12). 

One specimen fi-om 40 fathoms, Suvadiva Atoll. Rubble and broken coral bottom. 

Total length about 25 mm., total breadth about 15 mm. Tentacles from ant. margin 5 mm. 

Mouth aperture about 13 mm. behind anterior margin. Male gonopore about 5 mm. behind 

mouth. Female gonopore about 1 mm. behind male. 

Colour white with small pigmented patches, scattered rather numerously near the dorsal 

surface. Tentacles about 2 mm. apart, bilobed at the tips; each with a dense cluster of eyes 

at its base. Brain compact, lying under a median branch of the gut. There is a cluster of 

eyes over the brain between the tentacles (Fig. 61). 

—

THE MARINE TURBELLARIA. 283 

The epidermis is composed of very small cells, crowded with a finely granular secretion. 

I can find no trace of rhabdites. The basal membrane is thick, and occasionally pierced by 

processes from gland-cells, lying beneath the integu- 

ment. The muscle layers consist of a thin, outer, 

longitudinal layer, followed by two layers of diagonal 

fibres. These are succeeded by a circular layer 

which is much thicker on the ventral than on the 

dorsal side. Lastly on the ventral side only is an 

inner longitudinal layer. 

The pharyngeal aperture is median. From the 

main gut some seven pairs of gut branches are given 

off. These again ramify into numerous smaller 

branches as they run outwards. 

The small pigmented patches, referred to in 

the short account of the external characters given 

above, are found in section to be due to the pres- 

ence of dark bodies in certain remarkable, dorsal 

diverticula given off from the gut branches (PI. XV. 

..•• 

6r 

•« •• • 

ffut. 

Fig. 61. Eye-spots of Planocera armata. 

te. tentacles, br. brain. 

fig. 10). The gut branches themselves are lined with very elongated columnar epithelial cells 

lying on a delicate basal membrane from which they are fi-equently, in my sections at least, 

torn away. The epithelium of the diverticula on the other hand, though similar in appearance, 

is structurally much reduced and obscured by the dark bodies referred to above. 

These dark bodies are of three kinds. Firstly, there are numerous rather large, black, 

spherical bodies, which are evidently produced in the gut epithelium itself With a high power 

different stages of the development of these bodies are readily distinguishable. They commence 

as small, lightly-staining masses, which increase in size, and at the same time take a deeper 

stain. Of their ultimate fate nothing can be said at present. They are scattered pretty 

regularly through the gut tissue and probably have but little or no share in giving the diver- 

ticula their characteristic appearance. Secondly, in and about the diverticula there are small 

masses of little rod-shaped bodies, probably bacteria. These do not occur generally throughout 

the gut, but only in the diverticula themselves or in their immediate neighbourhood ; in 

the latter case they invariably have an appearance of streaming into the diverticula. Lastly, 

I have found in one or two diverticula only, a quantity of exceedingly fine, granular, pigment- 

like substances. 

The significance of these bodies and of the diverticula themselves is obscure. The latter 

may be compared directly with the gut diverticula of such a form as Thysanozoon hrocchii. 

Diverticula of a precisely similar character occur in a species of Planocera, as yet undescribed, 

collected by Mr Gardiner at Rotuma, whilst Lang's [9] figure of PI. villosa suggests very 

strongly that a similar feature occurs in this species, though it is true that Lang appears 

to regard the pigment patches as merely epidermal. 

Mention should be made here of the fact that von Plehn [10] has figured the occurrence 

of marginal pores opening from the gut in an undescribed Planoceroid. In the species described 

next the large spherical bodies of the gut epithelium are present, but there are no diverticula 

and neither of the other kinds of dark bodies.

284 F. F. LAIDLAW. 

Genital apparatus. The characters are shown somewhat diagrammatically in PI. XV. 

fig. 11. In the female system the accessory vesicle (a. v.) of the vagina is thread-like 

and extends back as far as the level of the female aperture ( $ ). After receiving on its ventral 

side the common duct from the two uteri (c. d.), the vagus (va.) follows a winding course 

through the enormous shell glands (s. g.), and runs into a large bursa copulatrix {b. c), whose 

lumen has many folded walls, appearing in part at any rate to be glandular. As in other 

typical members of the genus the terminal parts of the male apparatus are enclosed in an 

outer muscular sheath (o. s.), in which lie the penis and the prostate (pr.) as well as the 

duct. A remarkable feature of the penis, and one that separates this species sharply from 

other known Planocera, is the presence at the end of that organ of six large chitinous 

hooks (c. h.) and at its upper end of a chitinous ring or collar (c. r.). The lumen of the 

penis is lined by a very large number of small chitinous spines (c. s.). These vary from "05 

to '07 mm. in length. The space between the penis and outer sheath is occupied by a very 

loose parenchymatous tissue. 

Female organs. At its hinder end the accessory vesicle (a. v.) is difficult to trace 

owing to its extremely small size. The lining cells are not ciliated. As it passes forward 

it increases in size and a very few circular muscles appear about it. After receiving the 

short common duct (c. d.) from the uteri, which are also lined with non-ciliated epithelium, 

the vagina {va.), as it must now be called, continues to run forwards for some little 

distance. It then turns first ventralwards and then backwards. As it turns back it 

widens out so that its lumen is wide from side to side but narrow dorso-ventrally. In this 

part of its course it receives the secretion of the relatively enormous shell-glands (s. ^r.), 

which have a characteristic granular appearance and stain very lightly. The vagina continues 

to run backwards, passing right through the shell-glands until it lies right under the front 

end of the bursa. Here its lumen becomes circular in section. It now makes a Z-shaped 

turn ujjwards, and runs into the hinder end of the large bursa copulatrix {b. c). As the 

vagina passes into the bursa its lining epithelium undergoes a marked change. Up to this 

point it consists of a fairly well-defined, cubical epithelium with deeply staining nuclei, 

apparently non-ciliated. As it passes into the bursa it becomes irregular and much folded; 

the protoplasm stains more deeply, and the nuclei can with difficulty be distinguished. 

From its proximal, anterior end the epithelium lining the bursa {g. I.) retains these charac- 

ters almost to the gonopore, in the neighbourhood of which it merges into a columnar 

non-ciliated epithelium, continuous with the epithelium of the surface. The epithelium of 

the bursa is secreting very actively a remarkable ' glairy ' substance, which occupies nearly 

the whole lumen of the bursa. Outside this epithelium the bursa is built up of a thick 

muscle layer of circular fibres. The folding of the wall lining the lumen of the bursa is 

no doubt, as Lang suggests, to permit of the distension of the organ. The secretory character 

of its wall is, so far as is known, confined to this species, and without homologue in the 

bursa of any Polyclad I am acquainted with. This peculiarity combined with the very remark- 

able nature of the penis indicates that this species is one of the most specialized in the 

whole order. 

Male apparatus. The gonopore opens into an antrum masculinum whose walls closely 

resemble those figured by von Graff for his PL simrotlii [6]. Little spherical masses of granular 

secretion given off from the cells lining the antrum lie scattered in its cavity. The outer 

sheath (PI. XV. fig. 12, o. s.) is composed of two layers of muscle fibres, an outer longitudinal

THE MARINE TUKBELLARIA. 285 

and an inner circular layer. At its anterior proximal end it is pierced by the ductus ejacu- 

latorius running into it from the small muscular vesicula seminalis {v. s.). At the same end 

lies the large prostate gland (pr.), whose duct joins the ductus ejaculatorius some way before 

entering the penis. Retractor muscles run from the upper end of the penis, and from the 

distal jjart of the ductus to join the outer sheath. 

A transverse section through the distal lower limit of the penis is represented somewhat 

diagrammatically in fig. 13. The irregular lumen is seen to be lined with short chitinous 

spines (c. s.) and the section passes through the bases of the six large hook-like structures (c. h.). 

Outside the spines and hooks is a narrow layer of hyaline protoplasm, and beyond this the 

irregular, diagonal, intrinsic muscles of the penis (p. ni.) in close contact with the muscles of 

the outer sheath, here rather feebly developed. The small cavities (a. m.) are parts of the 

antrum masculinum. The irregularity of the lumen is probably due to shrinkage. Further 

forward a transverse section shows the hyaline layer rather more clearly defined, and outside 

it is a broad muscle layer composed of diagonal fibres which are closely packed together on 

the inside, but loosely arranged to the outside, so that no very clear boundary can be distin- 

guished between the muscles and the parenchyma, which have divided the intrinsic muscles of 

the penis fi'om those of the outer sheath. 

At the level of the chitinous ' collar-like ' structure the sections have unavoidably been 

torn. Consequently I cannot be certain of the relationship of the collar to the penis or to 

the retractor muscles, but some of the latter seem to be attached to it. The collar itself, 

seen in the animal when cleared in oil of cloves before it was cut into sections, appeared 

as a ring of chitinous material, its uf)per, anterior end wider than the lower, and its outer 

surface decorated with a rectangular sculpturing. On account of the tearing of the sections 

it is also impossible to say whether the ductus ejaculatorius entered the penis by passing 

through the collar or to the outside of it. 

In a transverse section in front of the penis but before the level of the prostate, the 

ductus ejaculatoi'ius can be seen running through the middle of the section. It has a narrow 

lumen lined with ciliated epithelium. Outside this is a thin layer of circular muscle fibres 

followed by a longitudinal layer. From this longitudinal layer a number of bundles of 

retractor muscles are given off, exactly similar to those connected with the hinder end of the 

penis itself In sections at this level many of them lie cut across obliquely amongst the 

parenchyma which here fills the wide space between the ductus and the outer sheath. The 

ductus runs nearly straight back to the prostate. Just before entering the latter it divides 

into a wider part running to the gland and a narrower part continuing to the vesicula 

seminalis, after piercing the wall of the outer sheath. It is interesting to find here a 

little peculiarity which evidently also occurs in PI. pellucida (see von Graff's figure [6]), 

i.e. the duct fi-om the vesicula does not open immediately into that fi-om the prostate, but 

is actually prolonged for a short distance inside it. This prolongation is probably of the nature 

of a valve. Each of these two parts making up the ductus ejaculatorius is provided only 

with circular muscle fibres; but, whereas those of the prostatic part are few in number, those 

of the part running to the vesicula though few at first increase rapidly in number as the 

vesicula is approached. 

The prostate (pr.) is a large gland, lying in close contact with the outer sheath at its 

anterior end ; in fact the circular muscles of the sheath completely enfold it, and form a muscular 

wall for it. On the inside it is lined with a much-folded glandular epithelium. The vesicula


seminalis lies outside the outer sheath. It is small, with thick muscular walls composed of 

circular fibres. The vasa deferentia before joining it are. much swollen and full of spermatozoa; 

they are lined with a cubical ciliated epithelium, and have no nuclei. The vesicula itself 

contains no spermatozoa. 

2. Planocera langii, sp. n. (PI. XIV. fig. 1, and PI. XV. fig. 13). 

One specimen fi-om Minikoi. " White transparent form." Body flat, oval ; margin 

folded. 

Total length about 20 mm. Front margin to mouth opening 11 mm. Front margin to 

male aperture 13'5 mm. Male to female aperture about "3 mm. Tentacles about 7 mm. fi-om 

the anterior margin, and about 1'5 mm. apart. 

Tentacular eyes numerous, small, lying at the base of either tentacle in a dense cluster. 

Tentacles slightly bilobed at their ends. Behind the tentacles is a single pair of small eyes, 

lying over the brain. Colour white, with a few small black chromatophores lying scattered 

round the pharynx region dorsally. There are in addition a number of exceedingly small black 

spots consisting apparently of pigment granules \'isible on the dorsal surface above the hinder 

part of the pharynx. These granules lie in the parenchyma, and are not of course comparable 

in any way to the diverticula described in the previous species. Similar granules occur in an 

undescribed species of Planocera from Rotuma. 

Genital apparatus. Aii examination of the accompanying Figure 62 shows that the 

present species differs strikingly so far as 

these organs are concerned fi:om PL armata. ^c 

In fact it seems impossible to homologize 

the bursa copulatrix of the one with that of 

the other. The female aperture (?) leads 

into a spacious antrum femininum into which 

the shell-glands (sh.gl.) open. From the antrum 

a short passage runs dorsalwards. It 9 sJ^~ 

quickly divides to form the vagina which ^ „, „ , 

' •' 

. I'lG. 62. Female apparatus of P/anocera tojû (diagrammatic). 

runs backwards, and the bursa copulatrix 

For explanation of lettering see text. 

(6. c.) which extends forwards alongside the 

penis, lying at rather a higher level than the vagina (see fig. 13). The latter after a 

short distance bends ventralwards, and at the same time receives the separate openings of 

the uteri (ut). Beyond this the character of its lining epithelium alters completely, and the 

organ is continued backwards as an elongated vesicle, which may be called the receptaculum 

seminis (?. s.), homologous with the accessory vesicle of PL armata. A remarkable feature of 

the male apparatus is the presence of a pair of vesiculae seminales, dilations of the terminal 

parts of the vasa deferentia with thick muscular walls. Compared with PL armata, this species 

has a long ' outer sheath ' with feeble walls. The penis is long and twisted, without retractor 

muscles. The chitinous spines lining its lumen are relatively few, and there are neither chi- 

tinous hooks nor ring. The penis extends right back to the level of the prostate, which com- 

municates with it by a short wide duct. 

Female organs. The receptaculum seminis (= accessory vesicle) is lined by a regular, 

columnar, ciliated epithelium, resting on a fine, basal membrane. All the nuclei lie at the lower 

extremity of their cells, close to the membrane. They have a lightly staining ground-substance 

with scattered chromatin granules. The protoplasm is faintly granular. The receptaculum lies


rather near the ventral surface. As it approaches the vagina it makes a sharp turn up and 

the appearance of the epithelium changes; circular muscle fibres make their appearance, and, 

after receiving the uterine openings, the organ is continued forward as the vagina, the epi- 

thelium here consisting of a short, columnar, ciliated facies. The nuclei are homogeneous 

and darkly-staining; the protoplasm is hyaline. The bursa copulatrix extends forward as far 

as the front end of the male apparatus. Its inner walls are much folded and lined with 

cubical non-ciliated epithelium. Outside this it has moderately thick muscular walls composed 

of circular fibres. The undescribed species from Rotuma, to which I have already referred, 

bears a strong resemblance so far as the female apparatus is concerned to PI. langii. In it 

the receptaculum seminis is crowded with spermatozoa. 

Male apparatus. The outer sheath consists in this species of circular fibres only. 

From the antrum masculinum for about a quarter of its length, which is roughly a millimetre, 

it is continuous with the intrinsic muscular wall of the penis, and traversed by scattered, 

radial fibres running fi-om the latter. 

After this a split appears between it and the intrinsic muscles of the penis, leaving a 

space round the latter. At the upper anterior end the prostate as in the other Planocera 

lies in close contact with the outer sheath. The few muscle-fibres surrounding the prostate 

do not seem to be derived from the outer sheath. Lastly the sheath is pierced at two 

points by the ducts running to the penis from the vesiculae seminales. 

The penis is approximately a millimetre in length. It is a cylindrical, tube-like organ, 

its lumen lined with chitinous spines, which are a little hooked and not very thickly set. 

The diameter is roughly equal throughout its entire length. The muscular wall consists of 

a well-defined, rather thick layer of circular fibres crossed by radial fibres. The penis is con- 

tinued right up to the level of the prostate, which communicates with it by a short, wide, 

muscular duct, opening into it at the same point as do the ducts from the vesiculae. 

At a point about one-third of the total length of the penis fi-om the male aperture 

the chitinous spines are interrupted by the appearance of two curious folds of the imier 

wall (PI. XV. Fig. 13, pL). These folds are margined with chitinous material. It is possible 

that they may be to some extent comparable to the chitinous hooks or collar of PL armata, 

but their function is quite unknown to me. Behind them the spines are continued again 

up to the level of the opening of the prostate duct. As already stated each of the vasa 

deferentia is dilated before entering the outer sheath to form a vesieula seminalis, and the 

dilated part has muscular walls composed of circular fibres. The ducts running' fi-om the 

vesiculae to the penis are also muscular. 

Before passing to consider the species belonging to the next family I may briefly notice the 

presence of a large Planoceroid represented by a single damaged specimen in the collection, 

which I am not able to describe. Its total length is probably about 45 mm. A pair of 

dorsal tentacles are visible. It is perhaps a Stylochoplana. I could only find indications of 

a single genital aperture, the genital organs being quite immature. 

Group. 

II. Family Leptoplanidae. 

3. Leptoplana pardalis, sp. n. (PI. XIV. fig. 9, and PI. XV. fig. 14). 

Several specimens from the reef, Goidu, Goifurfehendu Atoll, and from Minikoi, Laccadive 

G. 37


Average length about 48 mm. Eyes distant 10 mm. from the anterior margin. Mouth 

opening about 20 mm. from the anterior margin. The male aperture lies about a millimetre 

in front of the female, the latter is about 15 mm. from the hinder end of the body. 

The colour (in spirit specimens) is pale yellow. On the dorsal surface this is thickly 

studded with rosette-like clusters of brownish-black chromatophores. On the mid-dorsal line 

in the middle third of the back these chromatophores form a continuous band ; near the 

margin the clusters are replaced to some extent by single chromatophores. 

The eyes are arranged in two clusters of ' tentacle-eyes ' of moderate size, each containing 

about a score of eyes. In front of them lie on either side about as many more eyes 

scattered irregularly. The gut branches anastomose. 

This interesting species combines to some extent the characters of Discocelis with those 

of Leptoplana. The presence of a pair of receptacula seminis developed from the accessory 

vesicle of the vagina resembles the condition found in Discocelis tigrina, whilst the absence 

of marginal eyes and the widely separated gonopores forbid us to refer it to that genus. On 

the whole it is most conveniently placed in the genus Leptoplana as at present constituted, 

the male organs resembling those of other species of that genus. 

Female apparatus. (See Figure 63.) The vagina (va.) runs back from the female 

aperture ( $ ) and receives the common duct {c.d.) from the uteri. 

These latter extend forward from the short common duct, each being formed of two 

distinct sections. Firstly there is a duct-like part, 

consisting of a narrow tube lined with cubical, cili- 

ated epithelium, suiTounded by a few circular muscles 

(u.d.). This opens at about the level of the male 

aperture into a wide, irregular, glandular part, the 

pair extending forward on either side of the pharynx, 

and in one of the specimens, examined by sections, 

containing eggs. The walls of this glandular part 

(u.gl.) are much folded, and their epithelium is se- 

creting actively and full of globules of a finely 

granular substance. Cell outlines are not visible. 

Behind the entrance of the common duct from 

the uteri the vagina, whose lumen is lined by cubical, 

ciliated epithelium surrounded by circular muscle 

fibres, runs back for a short distance, and finally 

opens into a crescentic accessory vesicle (ace. v.) with 

its horns directed forward. From either horn a narrow 

duct (ace. d.) runs forward, ending in a spherical 

dilatation {r. s.) which probably functions as a re- 

ceptaculum seminis. The cubical epithelium, lining the accessory vesicle and the ducts opening 

into it, is not ciliated. In one specimen the receptacula are crowded with spermatozoa, 

surrounding a pass of what appears to be a granular secretion. 

Considerable interest attaches to this species in that the walls of part of the uteri 

themselves are glandular. Glands in connection with the uteri are as a rule only present 

in certain Cotylea, such as Diposthus, Pericelis and various Euryleptidae, where they occur in 

ace d 

Fig. 63. Female apparatus of Leptoplana pardalis 

(diagrammatic). For explanation of lettering see text.


diverticula from the uterus. The accessory vesicle on the other hand only occurs in the 

Acotylea. In Discocelis it is glandular. 

Male apparatus. The vasa deferentia dilate at their terminations to form a pair of 

moderately wide vesiculae seminales whose walls are surrounded by a thin layer of circular 

muscle-fibres. These vesiculae open into a short and narrow ductus ejaculatorius (PI. XV. 

fig. 14, d.e.) lined with ciliated epithelium and provided with rather thick muscular walls. 

This duct narrows suddenly as it enters the muscular penis (pe.), which projects as a bluntly 

conical muscular mass into the antrum {a.m.). The antrum is lined with non-ciliated 

epithelium and its walls are muscular, forming the muscle sheath ; I can find no trace of 

gland-cells in the epithelium. 

Amongst the six specimens of this species collected at Minikoi is one which differs from 

the rest in coloration, being much darker. After a careful examination I have come to the 

conclusion that this difference is chiefly due to the expanded condition of its chromatophores, 

though they may be slightly more numerous. Unfortunately it is not possible to say whether 

this specimen was collected under different conditions from the others. Since examining these 

specimens I have received from Mr Gardiner three others, which I believe to be specifically 

identical with them, from Funafuti in the Pacific. 

4. Leptoplana, sp. 

One specimen from Minikoi. Damaged. 

The arrangement of the eye-spots is that of a typical Leptoplana. There are a pair of 

small compact ' tentacle-eye '-groups, and in front of these the scattered brain-eyes. 

G-enital apparatus. The female aperture lies about two mm. behind the male, un- 

fortunately the hinder part of the female apparatus is missing, but it bears a fairly close 

resemblance so far as can be determined to that of L. vitrea as figured by Lang. The shell- 

glands are very numerous, their secretion takes the form of enormous numbers of minute 

rhabdite-like bodies, similar to those found in Pericelis (see below). These rhabdites can 

be seen making their way into the lumen of the vagina. In the neighbourhood of the 

terminal parts of the genital apparatus the unripe shell-glands are so numerous as to give 

the tissue a characteristic appearance. They resemble closely those of L. alcinoi figured by 

Lang ([9] T. 14, Fig. 2), but in the latter species they a.re pyi-iform, whilst in the species 

under consideration they are spherical. 

As they ripen and become filled with the small rhabdite-like bodies, the cell outlines 

become obscured, and finally the cells seem to disappear as though they had ruptured to permit 

of the escape of the contained rhabdites. 

The walls of the vagina are lined with ciliated epithelium, and, as it passes back from 

the antrum, a fairly strong muscle layer developes about it. After running for a short distance 

backwards the vagina turns upwards and a little forwards and then finally backwards, receiving 

the separate openings of the uteri. Thence it continues back, first as a narrow tube, but 

further back appearing to open into a wide accessory vesicle ; owing to the displacement of the 

organs at the hinder end of the body it is extremely difficult to follow. The uteri run 

forward, and for the first millimetre or so of their length have muscular walls, further on 

the muscles disappearing. 

37—2


In the male apparatus the vasa deferentia open into a muscular vesicula seminalis, 

resembling in shape that of L. vitrea. From the front end of the vesicula the ductus ejacula- 

torius runs backwards and downwards for some distance ; its lumen is rather wide and it is 

lined with glandular prostatic cells, outside which lies a layer of circular muscular fibres. 

This part of the apparatus resembles rather that of L. pallida than of L. vitrea. The rest 

of its structure is practically identical with that of L. vitrea. The duct narrows, and runs 

vertically upwards, then turns downwards and backwards again, extending parallel to the first 

part of its downward course. It is here very narrow, surrounded by a compact layer of 

circular fibres, outside which lie less compact, diagonal fibres. It opens finally into the antrum 

masculinum. These muscles form the penis. 

As this specimen is in an imperfect condition I cannot describe it fully, though I believe 

it to be quite distinct from any named species. 

III. Family Cestoplanidae. 

5. Cestoplana ? maldivensis, sp. n. 

A single specimen from the reef of Minikoi, Laceadive group. 

Total length about 15 mm., breadth 5 mm. Body flat, anterior end pointed, posterior end 

tapering a little. Colour (in spirit specimen) uniform dull brown. The 

hinder end of the body of the single specimen has unfortunately been 

so much damaged that it is impossible to determine the characters of 

the sexual organs. 

The pharynx has the position typical for Cestoplana, and the mouth 

opening is about 4 mm. from the hinder end, whilst the male aperture 

is certainly not more than 2 mm. from the extremity. 

From the two species of the genus previously known, viz. C. mhro- 

cincta (Grube) and C. faraglionensis (Lang), the present species is 

separated by its relatively short and wide body. Another more striking 

difference is afforded by the arrangement of the eye-spots. In C. mal- 

divensis there is a complete series of these round the margin of the 

body (see Fig. 64), on the posterior two-thirds of the body being few 

and distant, but on the anterior margin on either side as far back as 

the level of the brain thickly scattered. In addition to these in the 

apex of the triangular anterior end of the body lie a small number of 

eyes scattered over an area which stretches back for about half the 

distance from the apex to the brain ; and further from the middle of 

the hinder end of this area two irregular parallel lines, each of a single 

row of eyes, extend back as far as the brain, which lies at about the 

end of the first sixth of the body. 

The uteri can be traced forward through the hinder two-thirds of 

the body, and are crowded with eggs. Until it is possible to examine 

the genital apparatus of this species in a better-preserved specimen I 

prefer to leave it in the genus Cestoplana, although there can be no 

doiibt that it differs strikingly from typical members of that genus. 

Fig. 64. Cestoplana (?) 

maldivensis. x 7.

THE MARINE TURBELLAllIA. 291 

COTYLEA. IV. Family Pericelidae, nov. 

6. Pericelis hyerleyana (Coll.) (PI. XIV. fig. 6, & PI. XV. fig. 15, 16, & 17). 

Typhlolepta hyerleyana. Collingwood, Trans. Linn. Soc. Lond. (2) 

Monogr. p. 616. 

Five specimens fi-om Minikoi. 

i. p. 92; Lang, Naples 

Collingwood's description of this species is as follows :—" Length f inch, breadth | inch. 

Body smooth, thin, the lateral parts very ample and puckered. Upper surface beautifully marbled 

with light brown rings, including roundish spaces of a whitish colour, smaller rings being between 

the interstices of the larger; most crowded and darkest in colour along the median line, and 

more delicate towards the side. Under surface of a pale grey, the dendritic markings in the 

centre of an opaque white. Its movements were very contorted and it did not exhibit much 

activity. One specimen from under a piece of coral on Pulo Barundum off the west coast 

of Borneo." 

In Mr Gardiner's collection are five specimens agreeing with this description so far as 

it goes, save that three of them are of considerably greater size. They are however provided 

with tentacles on the anterior margin, and with eyes; but I believe that Dr Collingwood may 

well have overlooked these owing to the extreme folding of the edge of the body. 

Owing to the fact that this species possesses both eyes and tentacles it must be removed 

from the genus Typhlolepta. Its characters,, moreover, are such as to distinguish it from all 

other Cotylea sufficiently to make it the type of a new genus and family'. 

The family Pericelidae may be defined as follows :— " Cotylea with small widely separated 

tentacles, with a complete series of marginal eyes; penis single; pharynx central; margin of 

the body excessively folded." Genus Pericelis. 

The nearest ally of this interesting form is, I consider, Anonymihs, the only other Cotylean 

Polyclad in which there is a complete series of marginal eyes. Pericelis further has the an- 

terior margin notched in the middle line just as in Anonymus. 

The most striking feature of the species, when viewed with the naked eye, is the extreme 

folding of the margin of the body. In one of the larger specimens the length of the body 

along the middle line is 35 mm., and the breadth at its middle about 32 mm., whilst the 'rim' 

of the body when spread out is not less than 230 mm. in length. In this same specimen the 

small tentacles lie not less than 9 mm. apart. They are crowded with eyes, and eyes are 

scattered completely round the margin inwards for a depth of about 5 mm. In the middle of 

the anterior margin is a well-marked notch or indentation, about 5 mm. behind this in the 

middle line is the elongated cluster of brain-eyes. ' 

Other measurements are as follows :—mouth opening about 18 mm. behind the anterior 

margin. The male gonopore lies about 4 mm. behind the mouth. The female gonopore about 

2-5 mm. behind the male. Sucker 1 mm. behind the female orifice. 

To Collingwood's account of the coloration nothing need be added. I have ventured to 

give a coloured figure of one of Mr Gardiner's specimens to show the position of the tentacles 

and brain-eyes. It illustrates too the extraordinary amplification of the lateral parts of the 

body. 

' The species is evidently a widely distributed one. I have received recently a sixth specimen of it from Mr Gardiner 

from Kotuma in the Pacific.


The body is characterized by its tenuity, its average thickness is only from '3 to '4 mm. 

Along the middle line there is of course a considerable thickening over the pharynx and 

genital apparatus, forming a ridge such as usually occurs in a Polyclad. 

On the dorsal surface the epidermis contains large numbers of rhabdites about '01 mm. in 

length. These are absent from the ventral surface. In addition to the rhabdites, pseudo- 

rhabdites occur numerously in both the dorsal and ventral epidermis. They are pellet-like 

bodies composed of a coarsely granular material, and are rather longer and at the same time 

thicker than the rhabdites. They are of sufficient size and number to give the whole surface 

of the body a granular appearance when viewed with a simple lens. On the dorsal surface of 

the tentacles the character of the epithelium differs markedly from that found elsewhere (see 

fig. 17). No rhabdites and only a very few small pseudorhabdites occur, and the whole ejjithelium 

has a very regular columnar arrangement, the nuclei all lie at the same level, viz. at about 

the middle of the cell. The cilia are not modified in any way, nor does there appear to be 

any special sensory apparatus. On the ventral surface of the tentacles the arrangement of 

the epidermal nuclei is quite irregular, and pseudorhabdites are fairly numerous, though not 

so abundant as over the general surface of the body. 

The basal membrane lying below the epidermis is moderately thick; immediately below 

it lies the pigment, which to a great extent obscures the dorsal musculature. On the tentacles 

the pigment presents the appearance of being contained in chromatophores, whilst over the 

general dorsal surface of the body it is more diffuse and may be intercellular. In the 

flattened lateral parts of the body the inner longitudinal ventral muscle-layer is very 

strongly developed and extends dorsalwards for fully one-half of the thickness of the body. 

The muscles are but feebly developed in the tentacles; the space lying below the body- wall 

is almost entirely occupied with nerve-tissue. The " sucker " has its disc covered with a nonciliated 

columnar epithelium ; the nuclei are scarcely distinguishable, and the basal membrane 

very thin. Amongst the muscles below the basal membrane lie elongated gland-cells, full of 

a finely-granular secretion. Processes from these cells pierce the basal membrane and make 

their way through the epithelium to the surface. No pseudorhabdites are found in the epi- 

thelium of the disc. The pharynx is much folded and of considerable size, resembling in its 

arrangement that of Anonymus viridis. 

Genital apparatus. In the two specimens from which sections were prepared the genital 

apparatus was well developed (Fig. 65). The vagina (va.) is of the type usually found in 

the Cotylea; that is to say, it runs upwards from the gonopore ($), dilating at the point where 

it receives the shell-gland secretion {sh. gl.), further on narrowing again. It then turns back 

and downwards for a short distance, finally terminating in the uteri (ut). 

It is in connection with the uteri themselves that some of the most interesting characters 

of this species occur. In the first place there are a number of small rounded vesicles (ut. v.) 

each connected with the uteri by a short stalk-like duct. These vesicles in some cases 

contain quantities of spermatozoa, suiTounding what appear to be fragments of eggs (cf. Wood- 

worth [20], p. 66). In addition at intervals along the uteri are gaps in the walls, through 

which project into the lumen of the uteri cells, bearing a close resemblance to the yolk-cells 

of Dendrocoelum lacteum figured by Ijima [8] (see especially PI. XXI. figs. 7-10, loc. cit.). This 

character is of importance, as hitherto no Polyclad possessing any organs comparable to the 

Triclad yolk-glands had been described.


The penis is muscular and directed backwards. It is conical in shape, and tapers to a 

fine point, which projects into a long and extremely narrow antrum masculinum (a. m.). At 

its anterior, proximal end the penis re- 

ceives on either side the vasa deferentia 

{d. e.), crowded in the specimens with 

spermatozoa. 

Female apparatus. The shell- 

glands are large and extend for a con- 

siderable distance laterally. Their secretion 

is in the form of an immense 

number of minute, spindle-shaped, 

rhabdite-like bodies, which are each 

about a quarter of the size of the 

epidermal rhabdites. These are of pe- 

uf V 

Genital apparatus of Pericelis byerleyana (diagrammatic). 


culiar interest as bearing on the morphology of the rhabdites of Turbellaria, and strongly 

supports the view taken by Woodworth [19] and others. 

The vagina is narrow and lined with ciliated epithelium, surrounded by a very narrow 

layer of circular muscle-fibres, thicker at its hinder end, where it turns downward to receive 

the uteri the vagina has rather a thicker muscle layer. Outside the muscle-fibres lie a number 

of nuclei probably belonging to gland-cells. The epithelial lining of the uteri, if present, is so 

reduced that I have not been able to distinguish it. The walls of the uterus apparently 

consist of a ring of muscle-fibres surrounded as in the case of the vagina with gland-cells 

(see fig. 16). The uterine vesicles (see Fig. 65, xit. v.) are lined with a cubical, or somewhat 

columnar, non-ciliated, secretory epithelium. It rests on an extremely delicate basal membrane, 

and there is no muscular coat. The character of the lining epithelium of these vesicles recalls 

that of the receptaculum seminis of Planocera langii. 

The vesicles are connected with the uteri by ducts of varying length, some so short 

that the vesicle is almost sessile on the uterus (fig. 15). They are similar in structure to 

the uteri themselves but smaller. The vesicles are fairly numerous, eleven opening into the 

uterus of one side between the level of the mouth opening and the vagina. So far as I can 

find they do not extend forward in front of the mouth. As already stated these vesicles 

firequently contain spermatozoa, surrounding a ' 

lump 

' 

of material, which appears to consist 

of small, round, hyaline cells with black nuclei, which do not resemble eggs. In the homologous 

vesicles of Diposthus corallicola Woodworth and in certain Euryleptidae spermatozoa are found 

surrounding fragments of what Woodworth and Lang suppose to be eggs, but in the present 

instance these ' lumps ' are certainly not fragments of eggs. The ovaries contain ripe eggs. 

The oviducts themselves are indistinguishable. 

Certain remarkable structures, as has already been stated, occur in connection with the 

uteri which bear a fairly close resemblance to the yolk-glands of certain Tricladida. The only 

structure with which they can be compared in the Polyclads are the ' rosette-like glands ' of 

Cycloporios papillosus, described by Lang [9]. These differ firstly in that they open into the 

oviducts, and secondly in having the character of glandular diverticula fi"om the oviducts. In 

Pericelis on the other hand there are numerous gaps in the walls of the uteri (PI. XX. figs. 15 and 

16), through which project deeply staining pyriform cells, which do not seem to be of a definite 

secretory or glandular character, with oval black nuclei. On the whole these organs of Pericelis


approximate more closely to the yolk-glands of the Triclads than to any structure previously 

known amongst the Polyclads. It is possible, however, that they are connected with the cell- 

like bodies found in the uterine vesicles as described above. 

Male apparatus. The vasa deferentia are crowded with spermatozoa. They enter the 

walls of the penis some little distance behind its anterior end, narrowing as they do so. For 

the first third of its length its lumen is lined by glandular cells, and filled with a coarsely 

granular secretion (see Fig. 66). For the rest of its length it has a cubical ciliated epi- 

thelium, as also has the antrum masculinum. The wall of the penis is composed chiefly of 

circular fibres, interspersed with a few radial. The antrum becomes extremely narrow as it 

approaches the gonopore, and the latter is correspondingly minute. 

Fig. 66. Section across the base of the penis of Pericelis byerleyana. 

ê. = penis, pr. c. = glandular cells, v. d. =vasa deferentia, d.e. = va,s deferens entering penis. 

Leaving the specialized Prosthiostonium out of account I believe that all other Cotylea save 

Anonymus have a special muscular prostatic organ connected with the penis by a short duct. 

Consequently Pericelis is more nearly related to Anonymus in the structure of the terminal 

parts of this organ than to the rest of the Cotylea. 

V. Family P.SEUDOCERIDAE. 

7. Thysanozoon plehni, sp. n. (PL XIV. fig. 7, and PL XV. fig. 19). 

Three specimens " from the reef-flat " Minikoi, with " brown to slate-black papillae." 

Total length about 23 mm. Total breadth about 17 mm. ' 

Mouth opening ' about 5 mm. 

behind the anterior margin.


'plug-like' mass of tissue derived in part from the parenchyma and in part from the epidermis, 

which differs from the tissue surrounding it in being denser and in staining more deeply. It 

occurs in every papilla through which my sections pass, but I cannot 

offer any suggestion as to its significance. 

Behind the level of the pharynx, which resembles that of other 

species of the genus, the main gut gives off numerous branches. These 

do not all arise from it in the same plane, but at the same time no 

branches are given off from the ventral side. Von Plehn [10] in de- ^^^~^ T t 1 

scribing two new species, which she calls Thysanoplana indica and eyeso{ Thysamzoonplehni. 

Thysanoplana viarginata, pointed out that a similar peculiarity occurs 

in those species, but to a much greater extent, for in them apparently the branches may in 

addition originate from the ventral side of the main gut. I have also found—from a careful 

examination of a series of sections in the Laboratory Cabinet of the Owens College Zoological 

Department—that in the neighbourhood of the male aperture of Thysanozoon brocchii, and 

for some little distance behind it, the gut branches do not all rise in exactly the same plane, 

though only from the lateral walls of the main gut. It is in the same neighbourhood, viz. in 

that part of the body where the main gut is largest, that this feature is most marked in von 

Plehn's species of Thysanoj)lana as well as in Thysanozoon plehni. 

Genital organs. Excepting in detail these resemble very closely those of other species 

of the genus, and especially those of Th. auropunctatus (Coll.) as figured by von Stummer- 

Traunfels [14]. The terminal parts of the female ducts are in no way peculiar. The eggs, 

like those of other species of the genus, exhibit large centrosoma. 

Male apparatus. The vasa deferentia unite to enter the vesicula seminalis by a short 

common duct (" gemeinschaftlicher Einmiindungsgang " of von Stummer-Traunfels), which runs 

dorsalwards to open into the lower side of the vesicula near its hinder end. The vesicula 

extends forwards and a little downwards for the greater part of its length, but close to its 

anterior end it curves suddenly downwards and narrows into the duct to the penis. This duct 

is long, more than twice the length of the vesicula, and after a tortuous course enters the 

base of the penis, where it is joined by a very short duct running from the small prostate 

gland, which lies close above and behind the penis. It is lined with secretory epithelium, and 

has a compact muscular wall composed of diagonal fibres. The penis is armed with a short 

tubular chitinous stylet and projects into a cavity, whose walls form the penis-sheath. This 

cavity opens immediately below the penis into the antrum masculinum, which in turn ojjens 

to the exterior by the male gonopore. 

It is of some interest to find that, whereas the gonopore is situated on the middle line, 

the penis with the penis-sheath lies very decidedly to one side of it, the right side. But the 

cavity of the antrum is extended fairly equally both to the right and to the left of the middle 

line. This peculiarity perhaps indicates that this species is descended from a form in which, 

as in many other species of Thysanozoon, the penis is paired, and that one of the pair, the 

left in this instance, has disappeared leaving the right penis to open unsymmetrically into the 

symmetrical antrum. In Lang's Monograph, T. 30, fig. 17, a diagrammatic figure is given of 

the terminal male apparatus of Pseudoceros maximus—a species belonging to a closely-allied 

genus—which possesses a pair of penes. If we picture one of these penes to be atrophied, the 

diagram would represent very closely the appearance seen in a section of the present species 

passing through the penis and antrum masculinum. 

G. 38


Thysanozoon plehni is on the whole most closely related to Th. obscurum described by 

von Stummer-Traunfels [14] from Amboina. 

A. Forms with a pair of penes. 

Genus Pseudoceros. 

8. Pseudoceros gardineri sp. n. (PL XIV. fig. 4). 

One specimen from Hulule, Male Atoll. 

Total length about 35 mm., total breadth about 22 mm. Mouth opening 8 mm. behind 

the anterior margin. Female gonopore about 5 ram. behind the mouth. Sucker 7 mm. behind 

the female gonopore. 

The margin is much folded. Body flat, oval with a prominent mid-dorsal longitudinal 

ridge. Colour: dorsal surface a delicate gray with scattered irregular 

black marks of varying size dotted over the surface; under surface 

grayish-white. 

The marginal tentacles are sharply pointed, large and prominent. 

The eyes, which are exceedingly numerous, are grouped as follows. 

A large compact cluster containing about 200 eye-spots lies over 

the brain. This is circular in shape save for a slight notch in the 

middle of its hind margin. On the dorsal surface of either tentacle 

near the middle line and close to the anterior margin is a group 

of eyes, rather more scattered than those of the brain-cluster. On 

the outer side of each of these clusters is a second still more diffuse 

group. On the ventral surface of the tentacles, almost immediately 

under the more medially placed dorsal group, are two roughly square 

compact patches ; from the outer side of each of these a small 

' wing ' runs on to the ventral side of the tentacles (Fig. 68). The 

projecting ' wing 

' is concealed by marginal folds. 

9. Pseudoceros punctatus sp. n. (PI. XIV. fig. 5). 

One specimen from Hulule, Male Atoll. 

Total length about 30 mm., breadth about 17 mm. Mouth about 5 mm. from anterior 

margin. Female gonopore 4 mm. behind mouth. Sucker 4 mm. behind female gonopore. 

Body oval, flat, with well-marked, median, longitudinal ridge. Colour pale grayish-yellow, 

plentifully spotted on the dorsal surface with small black chromatophores. 

The tentacles are pointed as in the preceding species. 

The eyes over the brain form a very small cluster of some 25—34 minute eyes. At 

the base of each tentacle, on the dorsal side and close to the anterior margin, is a small, 

ill-defined cluster of eyes, and there are also a few scattered eyes on the outer sides of the 

tentacles. On the ventral side of the tentacles are a pair of small clusters near the middle 

line and a few scattered eye-spots along the tentacle fold. 

The species is readily distinguished from the preceding by its possessing much more distinctly 

defined and more regular chromatophores, as well as by the relative fewness of its eyes. It 

yet resembles it especially in the shape of the tentacles, which are more like those found 

in certain Euryleptidae than those of most Pseudoceridae. 

FiQ. 68. Ventral surface of 

Pseudoceros gardineri. 

p/i. = pharynx, s. = sucker, 

u(. = uterus, i i = penes, 

? = female aperture.

B. Forms with a single penis. 

10. Pseudoceros gamblei sp. n. (PI. XV. fig. 18). 


Several specimens from Minikoi, Laccadive Group, ' milk-white ' or ' transparent flesh colour 

with purple or dark-blue rims. 

Total length about 12 mm., breadth 6 mm. Mouth opening about 2 mm. behind the 

anterior margin. Female aperture about 1 mm. behind mouth. Sucker about 1 mm. behind 

the female aperture. 

A small circular cluster of eye-spots lies over the brain about 1"2 mm. behind the anterior 

margin. There is a row of eyes along the margin of the 

tentacles both on the dorsal and ventral sides, which is con- 

tinuous across the middle line (Fig. 69). 

Sections were cut transversely through the anterior region 

of the body of a semi-adult specimen. Rhabdites appear to be 

absent in the epithelium, and the muscle layers of the body- 

wall are feebly developed. The testes lie, as is usually the 

case, on the ventral side of the gut, and the ovaries which are 

immature can be recognised on the dorsal side. The penis is 

that of a typical Pseudoceroid. The vasa deferentia before 

uniting to form the muscular ductus ejaculatorius are each 

dilated to form a vesicula, which is crowded with spermatozoa 

(PI. XV. fig. 18). 

A feature of the species is the curious shape of the 

pharynx, which has its hindmost folds produced backwards to 

form wing-like projections on either side, extending as far back 

as the level of the female aperture (Fig. 69). 

11. Pseudoceros tigrinus sp. n. (PI. XIV. fig. 3). 

One specimen from Minikoi, Laccadive Group. 

ire 

Fig. 69. Anterior end of Pseudoceros 

gamblei. A. from ventral ; B. from 

the dorsal side. 

p7i. = pharynx, bT.e. = ' brain-eyes,' 

s. = sueker, J = penis, ? = female 

aperture. 

Total length about 17 mm., breadth 11 mm. Mouth aperture about 4 mm. from anterior 

margin. Male aperture about 5 mm. from anterior margin. Sucker about 3 mm. from male 

aperture. 

Ground colour orange-pink, margin and tentacles black. 

On the dorsal side, on either side of the middle line a black band runs from the anterior 

margin to within a short distance of the posterior margin. These two bands meet each other 

across the middle line at their anterior and posterior extremities. In addition to these black, 

triangular patches project inwards at intervals along the margin ; these like the two median 

bands have on them a few rather large, circular, pink spots, and between these the black is 

thickly flecked with very small white spots. 

The position of the eye-spots is completely concealed by the pigmentation of the body, 

which readily serves to distinguish the species. 

The remaining specimens referable to this genus, some eighteen in number, are all very 

similar to one another in appearance, being of black colour with yellow margins. Two distinct 

38—2 

' 

B


forms can be recognised. The first of these has a narrow pale yellow border and its ground 

colour is a greenish-black. The second has a broader orange border and its ground colour 

is rather a velvety-black. 

Excepting for the above difference it is difficult to find any distinguishing characters. 

Measurements are of little value owing to the varying degrees of contraction of the several 

specimens, and the dense pigmentation makes it impossible to determine the arrangement of 

the eye-spots, especially those of the tentacles, with any degree of accuracy. 

I believe the form with the pale narrow yellow margin is identical with Proceros biiskii 

of ColLingwood, found by him in Singapore Harbour. In his description [4] he gives the 

colour of the body as a rich velvety olive-green, but in his figure the body is shown rather 

as black. The appearance of the margin in his figure of Proceros huskii agrees with that of 

my specimens. I feel therefore justified in identifying them with Collingwood's species. 

12. Pseudoceros huskii (Collingwood). 

Proceros huskii Collingwood [4], p. 91, PI. I. fig. vi. 

Pseudoceros huskii Lang. Naples Monogr. p. 547. 

Ten specimens from Hulule and Minikoi. 

Length about 22 mm. Breadth about 12 mm. Mouth opening 5 mm. behind anterior 

margin. Sucker 8 mm. behind mouth. 

Colour black or greenish-black with a narrow pale-yellow margin. Eyes on the tentacles 

and in a small cluster over the brain; only visible in sections. 

The other eight specimens which have a broad orange margin are I think allied to 

P. huskii on the one hand and on the other to P. velutinus Lang, a species recorded fi-om 

Ceylon. I think it advisable to refer them for the present at any rate to a new species 

under the name of Pseudoceros flavomarginatus. 

13. Pseudoceros flavomarginatus n. sp. 

Eight specimens from Minikoi, Laccadive Group. 

Length about 25 mm. Breadth about 15 mm. Mouth aperture about 5 mm. behind the 

anterior margin. Sucker about 7 mm. behind the mouth. 

Colour velvety-black with an orange margin about 1'5 mm. wide. 

Eye-spots occur on the tentacles and over the brain. 

It will be noticed that this species is a little longer than P. huskii and that perhaps 

the relative position of certain organs is different. But, as already remarked, much importance 

cannot be attached to measurements. 

VI. Family Prosthiostomidae. 

14. Prosthiostomum elegans sp. n. (PI. XIV. fig. 8, PI. XV. fig. 20). 

A single specimen, dredged off hard sand, at 30 fathoms, in the lagoon of Suvadiva Atoll. 

Length of body about 18 mm., breadth 4-5 mm. Anterior margin rounded, posterior end 

of the body pointed. 

Colour, in the spirit-specimen, pale primrose-yellow. From immediately behind the level 

of the brain, on either side of the longitudinal mid-dorsal ridge, extends a row of chocolate-


brown chromatophores, about 12 in each row. In addition to these there is a single small 

chromatophore on either side of the brain (see PI. XIV. fig. 8). Under surface entirely prim- 

rose-yellow. 

A number of minute eyes are scattered round the anterior margin of the body. There 

are also two groups lying over the brain. These form a V-shaped cluster; the apex of the V 

is directed forwards, and each of its limbs, narrowing from behind forwards, is made up of 

some 15 eye-spots, which are rather larger than those of the margin'. 

The margin is not folded. In shape this species approaches P. dohrni, Lang, and its 

structure is closely similar to that of P. siphnnculus (Delle Chiaji), fully described by Lang. 

It differs however sufficiently from both and from other species admitted by Lang in colour 

and in details of the arrangement of the eyes. 

It was necessary to examine the specimen by serial sections. I append some details of 

its anatomy : 

— 

Body-wall. The epidermis consists of a columnar ciliated epithelium, containing but few 

rhabdites. It rests on a moderately thick basal membrane. The musculature of the body-wall 

is more strongly developed on the ventral than on the dorsal side. Immediately within the 

basal membrane lies a thin layer of longitudinal muscle-fibres, next to these circular fibres 

followed by diagonal fibres. Lastly, on the ventral side only is an inner longitudinal layer. 

Pharynx. The pharynx is of course tubular as throughout the family. My sections were 

only cut a little further forward than the proximal end of the pharynx, and at this end its 

lumen is triradiate in transverse section (Fig. 70, A), This triradial appearance occurs in other 

species of the genus). It shows some differences in detail from the proboscis of P. siphunculus 

described by Lang [9]. 

The outer and inner walls are lined with extremely flattened pharyngeal epithelium (Fig. 

70, B, 0. e. and i. e.). A large number of radial fibres {ra. m.) extend right across the wall from 

Fig. 70. Transverse section through the pharynx of Prosthioslomum elegans. 

A. An entire section showing the triradiate lumen. B. Part of the same more highly magnified. 


the inner to the outer epithelium. Immediately within the outer epithelium (o. e.) is a narrow 

layer of longitudinal muscle-fibres (e. I.), succeeded by a much wider circular layer (e. c). In 

P. siphunculus this circular layer is succeeded by a longitudinal layer, which Lang calls the 

retractor muscle layer. This layer is present in P. elegans, but is only poorly developed 

(m. I.). Amongst the fibres composing it occur a certain number of ganglion cells (g.). Below 

' In fig. 8 the marginal eyes are drawn proportionately too large.


the inner pharyngeal epithelium (i. e.) is a thick inner circular muscle layer (t. c.) followed 

by a narrower inner longitudinal layer (i.L). Between this latter and the median longitudinal, 

or retractor muscle layer (m. I.) lie the salivary glands {sa. gl.), occupying fully one-half the 

width of the proboscis. Whilst passing through these the radial muscle-fibres are gathered up 

into more or less compact bundles. 

Gut. The gut-diverticula are precisely similar in structure and arrangement to those of 

P. siphunculus. Their walls are crowded with exceedingly minute bacteria-like structures, which 

are entirely absent from other parts of the body. In the main-gut, 

however, I have found what appears to be a distinct kind of bacterial ^Mj^ M^ _ 

organism in various stages of growth (Fig. 71). The smallest, pre- ^^^ î|^ ^ \ 

sumably the youngest stages, are rod-like; as the organism increases ^j^ 7^ Bacteria-like oiRanism 

in size it gradually acquires a dumb-bell appearance, until finally it from the gut of Prostkiosto- 

consists of two nearly equal sub-spherical masses united by a short mum ehgans. 

stalk. Its subsequent fate I have not been able to trace. 

Genital apparatus. Of the female organs only the vagina and shell-glands are de- 

veloped ; they are precisely similar to those of P. siphunculus, and in fact of most Cotylea. 

The male organs are in full functional activity. In this species the relative size of the ter- 

minal parts of the male apparatus is much greater than in P. siphunculus, otherwise they are 

very similar in the two species. 

The two large vasa deferentia run inwards and forwards at their distal ends to open into 

the vesicula seminalis, a large sac with muscular walls, composed of circular fibres, lined on 

the inside with a flattened epithelium. The vasa deferentia do not open into the extreme 

hind end of the vesicula, but pass into its walls on either side a short way in front of its 

hinder extremity, and then run backwards in its walls for a short distance before opening 

into it. This arrangement may act as a valve to prevent 'regurgitation' of the sperm, when the 

vesicula is contracted suddenly. From the anterior end of the vesicle a ductus ejaculatorius runs 

forward to enter the penis. It is lined on the inside with a flattened non-ciliated epithelium, 

outside which is a very thin layer of circular fibres. 

Immediately in front of the vesicula, lying side by side above the ductus, are two large 

spherical vesicles with thick muscular walls composed of circular fibres; outside the muscular 

layer is a sheath of specialized parenchyma, rather denser than the ordinary tissue. These 

vesicles are called by Lang 'accessory vesicles.' Their lumen, which is fairly spacious, is 

lined with a flattened epithelium, bearing a few cilia. Each is provided with a short duct 

— relatively much shorter than in P. siphunculus—which runs forwards, twisting greatly as 

it goes, lying for the most part dorsal to the ductus ejaculatorius. These accessory ducts, as 

they may be called, differ greatly from the latter. They are in the first place much narrower, 

they have a relatively thicker outside wall of circular fibres, and the epithelium through 

which they run is tubular, that is to say the ducts are intracellular. They pierce right through 

the muscular coats of the accessory vesicles. " Sie sind innen von einem verschwindend nie- 

drigen Plattepithel ausgekleidet, in welchem die Zahl der einzelnen Epithelzellen andeutenden 

Kerne so gering ist, dass auf einen Querschnitt des Canales nie mehr als ein Kem zu liegen 

kommt, so dass man hier auch von durchbohrten Zellen sprechen kann." (Lang [9], p. 27(3.) 

The ductus ejaculatorius (which for convenience I will simply call the ductus) as it ap- 

proaches the base of the penis is joined by the two accessory ducts, which enter its walls and 

run forward in them for some distance, lying immediately to the outside of the epithelium of


the ductus itself. After entering the penis the two accessory ducts open into the ductus. The 

penis is curved downwards and a little backwards ; it consists essentially of the end of the 

ductus, protected by a tapering chitinous tube or stylet, with a narrow lumen, projecting into 

the antrum masculinum. It can be protruded and withdrawn through the male gonopore by 

the action of muscle-fibres, attached to the base of the chitinous stylet. 

The antrum consists of a small dorsal and a much larger ventral chamber separated from 

each other by a circular fold of its wall. The roof of the dorsal chamber is of course formed 

by the attachment of the basal part of the penis to the body. Its walls are lined with a 

flattened non-ciliated (?) epithelium, through which the secretion of a large number of gland- 

cells is being poured. These gland-cells lie beneath the epithelium, and may collectively be 

called the prostate glands. The walls of the dorsal chamber form the ' penis-sheath.' The 

ventral chamber of the prostate is lined with ciliated epithelium continuous with that of the 

surface of the body. Its walls have a muscular coat, consisting of an inner circular and an 

outer longitudinal layer of fibres. 

The accessory vesicles are both full of the coarsely granular secretion (fig. 20, s.) of the 

gland-cells of the dorsal chamber of the antrum, and the same secretion is present in the 

accessory ducts. This secretion cannot be the product of the accessory vesicles themselves, and 

must reach them through their ducts. But it can only enter the ducts by passing from the 

antrum through the external opening of the penis stylet, and travelling up the penis to the 

opening of the accessory ducts into the ductus, and then turning down there. This Lang ob- 

serves can come about in one of two ways. We may suppose that the secretion may be 

driven up the accessor*- ducts by contraction of the walls of the antrum, the male aperture 

and the ductus behind the openings of the accessory ducts being closed ; or the secretion may 

be drawn into the accessory vesicles by a pumping action of the vesicles themselves. The latter 

is perhaps the more probable method'. 

The species appears to be most closely related to von Plehn's P. nationalis from the coast 

of Labrador [11]. 

15. Prosthiostomum cooperi sp. n. (PI. XIV. fig. 2). 

Two specimens, one semi-adult, the other immature, from Hulule, Male Atoll. 

The larger individual is 17 mm. long and about 5"5 mm. broad. 

Colour, milky white, margin of the body much folded. The adult has a series of fine 

black circular markings, arranged roughly in two parallel rows running down the middle of 

the back, from immediately behind the brain eyes, almost to the end of the body. 

The anterior margin is rounded, the posterior pointed. The anterior marginal eyes are 

numerous and extend back along the margin considerably beyond the level of the brain eyes. 

These latter are arranged in two long, almost parallel series, which diverge slightly from each 

other at their ends. 

Body-wall much as in P. elegans, but the rhabdites are much more numerous. 

Genital apparatus. In both specimens the female organs are undeveloped. In the 

semi-adult the male apparatus is mature, but unfortunately rather displaced owing to the 

specimen having been damaged. 

' An examination of Lang's diagram of the genital organs account to be much more easily followed, see Lang [9] T. 30, 

of Prosthiostomum sipliunculus will enable the foregoing fig. 20.

302 F. ¥. LAIDLAW. 

The general arrangement of the terminal organs is similar to that in P. elegans, and the 

relative size of the parts is equally great. The vesicula seminalis lies transversely; this is 

probably owing to displacement. Its lumen, like that of the accessory vesicles, is relatively 

very small and the walls thick. The vasa deferentia unite before entering the vesicula, which 

lies transversely in the body possibly owing to displacement. The two accessory vesicles lie 

closely pressed together, and are bound up in a common sheath of specialized parenchyma. 

The glandular cells of the dorsal chamber of the antrum are well developed, but there is no 

secretion present either in the accessory vesicles or ducts. 

The following table records the distribution of known species of this genus : 

—


Eye-spots (see Fig. 72) much as in G. rubrocincta, but the hinder margin of the eye- 

bearing area is straighter.] 

II. NOTES AND CONCLUSIONS. 

Most of the species described above have been examined by means of serial sections, the 

only satisfactory method of dealing with preserved specimens of this group. In some cases, 

however, I found it practicable to diagnose species sufficiently without having recourse to sections. 

This was especially the case with various specimens belonging to Pseudoceros. 

I have not attempted to deal at all fully with the anatomy of any specimen described in 

the foregoing account, partly because space did not permit of my doing so and partly because 

Lang's Monograph has rendered it unnecessary. For fuller information concerning the anatomy 

of certain species of Planocera reference may be made to von Graff [6], and a very full account 

of the genus Thysanozoon has been given by von Stummer-Traunfels [14]. 

Planocera and a new Genus. Lang divides the genus Planocera as defined by him 

into two groups, A and B. These groups may briefly be defined as follows: 

A. Five to seven pairs of branches from the main gut. Penis cylindrical, its lumen 

lined with chitinous spines ; lying in a muscular outer sheath. Female apparatus 

provided with a muscular bursa copulatrix. 

B. Gut branches numerous. Penis styliform ; no bursa copulatrix. 

The really striking anatomical distinctions between the two groups argue equally marked 

physiological differences. That such exist is, I believe, shown by the fact that Wheeler [16] 

has proved that in PI. inquilina, a species belonging to group B, hypodermic impregnation 

frequently occurs, in fact that in some cases the vagina may have no function other than that 

of a passage for the escape of fertilized eggs. A similar phenomenon may occur in other members 

of group B. On the other hand in group A the structure of the penis would preclude the 

possibility of h}'podermic impregnation, whilst the presence of a large muscular bursa copulatrix 

indicates that fertilization is the result of a 

normal process of copulation. Such differences 

are quite sufficient to warrant the raising of 

the two groups to generic rank. The name 

A,' whilst 

I venture to suggest the name 

Planocera must be retained for ' group 

for ' group B ' 

Hoploplana. 

In Fig. 73 copied from Lang the arrange- 

ment of the genital organs of Hoploplana in- 

signis is shown. If this figure be compared with 

PI. XV. fig. 12, the difference between a true 

Planocera, such as PI. armata, and Hoploplana 

will be apparent. 

The genus Planocera then as restricted may 

be defined in the same terras as group A is defined above, as Planoceroids with—Five to seven 

pairs of branches from the main gut. Penis cylindrical, its lumen lined with chitinous spines; 

lying in a muscular outer sheath. Female apparatus provided with a muscular bursa copulatrix. 

G. 39 

KS 

Fig. 73. Genital apparatus of Hoploplana inaignis (after 

— 

Lang). tia.= vagina, «t. = uterus, sft. 3;. = shell-gland, 

v.s. = vesicula aeminalis, p.s. = penis, d. e. = ductus ejacu- 

latorius.


It is obvious that PL langii differs more from any one of the other Planucera than they 

differ amongst themselves. The most pronounced differences are of course for the male apparatus 

the presence of paired vesiculae seminales, for the female the character of the bursa copulatrix, 

which appears to develope as an outgrowth from the vagina. I am inclined to suppose that an 

organ of a similar character occurs in Veri-ill's genus Heterostylochus [15]. In describing it he 

says of the female organs that, " a long narrow median duct runs far forward from the female 

orifice and expands into a flask-shaped seminal receptacle or spermatheca near the male organs; 

a swollen egg-duct also connects with the female orifice." The spermatheca may perhaps be 

the same organ that I have called the bursa copulatrix. Its true character may be judged 

from its appearance as shown in PI. XV. fig. 13. 

Thysanozoon and Thysanoplana. Von Stummer-Traunfels [14] has recently suggested 

a modified definition of the genus Thysanozoon Grtibe : " Pseudoceriden mit spitzohrahnlichen 

faltenfbrmigen Randtentakeln, mit zottenfdrmigen dorsalen Anhangen in welche bisweilen Diver- 

tikel der Darmaste hineintreten, ohne jedoch daselbst auszumtinden : mit einfach oder doppelten 

mannlichen Begattungsapparate." 

The genus is thus made to include a number of tropical species, several new species being 

described in an interesting review of the genus by this author, who has also given a series 

of beautiful figures of most of the species. He finds that of all the species known to him only 

one, viz. Thysanozoon brncchii, has the dorsal papillae invaded by gut-diverticula. Thysanozoon 

brocchii and about six other species have paired male apparatus. Th. auropunctatus (Kel. Coll.) 

and several others have an unpaired penis. 

Von Plehn [10] has described a new genus, Thysanoplana, containing two species evidently 

closely allied to Thysanozoon. It is separated from this genus on the following grounds. Firstly, 

" Im Gegensatz zu Thysanozoon der mannliche Apparat ist unpaar." Secondly, " Hauptdarm mit 

zahlreichen vielfach tibereinander entspringenden Darmastwurzeln." The papillae are stated 

definitely to be invaded by gut-diverticula. 

Now if we accept von Stummer-Traunfels' amended definition of the genus Thysanozoon, 

it is evident that the first of the characters, viz. the unpaired male apparatus, will not serve 

to distinguish Thysanoplana fi-om Thysanozoon, and as to the second I have found that a similar 

peculiarity, though much less marked, occurs in Thysanozoon plehni (mihi), whilst traces of the 

same occur even in Thysanozoon brocchii (see above). Accordingly in this case the generic 

name Thysanoplana cannot, I think, be maintained. 

On the other hand, if we do not accept the amended definition and retain Thysanoplana, 

it will be necessary to subdivide Thysanozoon into several genera as follows : 

A. Species with gut-diverticula in papillae. 

a. Penis unpaired {Thysanoplana). 

b. Penis paired {Thysanozoon brocchii). 

B. Species without gut-diverticula. 

a. Penis unpaired {Thysanozoon plehni, etc.). 

b. Penis paired {Thysanozoon, sp.). 

The mode of origin of the gut-diverticula cannot, I consider, be employed as a generic 

character. On the whole it is simplest at present to refer all the described species to the 

—

genus Thysanozoon , and 


consequently Thysanoplana must be referred to the synonymy of that 

genus. When it becomes advantageous to divide up the genus, the best guide to a correct 

grouping of the species will probably be found in the presence or absence of gut-diverticula 

in the dorsal papillae. 

Distribution in the Indian Ocean. Great interest attaches to Mr Stanley Gardiner's 

collection owing to the fact that it is not only the first made in the neighbourhood of the 

Maldive and Laccadive Archipelagoes, but also that it is one of the largest ever made in the 

Indian Ocean ; certainly the largest since the publication of Lang's Monograph. It is not of 

course possible on our present knowledge of exotic forms to discuss the distribution of marine 

Turbellaria, yet a few points are worthy of remark in connection with these specimens. 

Firstly, it will be noted that the Euryleptidae are entirely lacking in the collection. We 

must not assume therefore that they are altogether absent from the reefs of the Archipelago, 

but we are certainly justified in supposing them to be of considerable rarity in that neigh- 

bourhood. This is the more remarkable when we remember that the Euryleptidae are well 

represented on the coast of Ceylon, and are known to occur in most seas. 

I quote here an extract from Mr Gardiner's notes : " I have no lists, nor can I find any 

account of the Turbellaria round continental tropical coasts, on which to base any comparisons 

as to the relative abundance of the group in the Maldives. From a limited examination of 

some reefs at Weligama and off the Jaffna coast of Ceylon I am inclined to think that they 

are very much less abundant in the Maldives, both in number and variety of species." 

Secondly, the relatively high percentage of Pseudoceridae in the collection is striking. In 

addition to the five or six species of Pseudoceros given in the systematic part there are frag- 

ments of a specimen, which must I believe be referred to this genus, but is too much broken 

to describe. 

Probably the Prosthiostomidae and Cestoplanidae will prove to be abundant over the 

whole of the Indian Ocean, and we may expect to find, especially in the latter family, forms 

of great interest. I have in my possession a collection of Turbellaria made by Mr Evans 

near Penang. This collection contains not less than two new Cestoplanoids, one of them 

a very remarkable creature with a complete series of marginal eyes which are much more 

numerous than those of Cestoplana maldivensis; its body also is relatively much longer. 

Lastly, the occurrence of Pericelis byerleyana and of Leptoplana pardalis in the Tropical 

Pacific as well as in the Maldives' Archipelago is of interest. Two other widely distributed 

species, Leptoplana tremellaris and Thysanozoon brocchii, are known, but both of these occur in 

north temperate as well as in tropical seas. 

Parasites. In none of the specimens in this collection, of which I have cut serial 

sections, have I found any gregarine parasite such as that which is found commonly in 

Leptoplana tremellaris^. On the other hand I would call special attention to the occurrence 

in two species, viz. Planocera armata and Prosthiostomum elegans, of bacteria or bacteria-like 

structures, which in both cases, but especially in the former, appear to occur only in certain 

definite situations. 

GuT-DlVERTlCULA. Similar gut-diverticula to those found in Planocera armata occur also 

in other Planoceroids. Whilst moi-phologically they are not unlike the diverticula which invade 

' I have not been able to identify this species. Discocelis tigrinia is infested with Ophiodina discocelidk Mengazzini, 

which is probably closely allied to it. 

39—2


the dorsal papillae of Thysanozoon hrocchii, it may be questioned whether their function is 

similar. In T. brocchii on the one hand these diverticula may assist in the aeration of the 

tissues. In Planocera armata on the other hand it is difficult to suppose that they can have 

this function ; I think it possible that they may rather be concerned in some way with nitro- 

genous secretion. 

The function of the dorsal papillae of certain species of Thysanozoon, which contain no 

gut-diverticula, is also obscure. In Thysanozoon plehni the curious plug-like mass of tissue at 

the upper end of the diverticulum is to some extent suggestive of being connected with the 

function of excretion. 

Relationships of the Cotylea. In dealing with Pericelis, Thysanozoon and Prosthiostomum 

in the systematic part of this paper I have given a fairly full account of the male 

genital apparatus of each, so that it is possible to compare and contrast the three chief forms 

that this organ assumes in the Cotylea. The arrangement of the eye-spots in Gestoplana mal- 

divensis and Pericelis byerleyana completely round the margin of the body is so far as at 

present known only paralleled in Anonymus virilis, Gryptocelis, and perhaps in Heteroplana 

newtoni. I believe that this marginal distribution of the eye-spots is to be regarded as a 

primitive character derived from a radially symmetrical ancestor. 

In the Cotylea other indications of a radial structure are most strongly developed in 

Anonymus virilis. Such indications are the sub-central mouth and the numerous male organs 

grouped around the single female aperture. The presence of organs in this species bearing 

a general resemblance to nematocysts is probably also an ancestral character, so that if we 

adopt the usual theory and assume that the Polycladida are derived from an ancestor possessed 

of radial symmetry we are justified in regarding Anonymus as nearer to this ancestral form 

in certain respects than are the other Cotylea. 

Intermediate between Anonyvius and the higher Cotylea stands Pericelis byerleyana, the 

most interesting type in Mr Gardiner's collection. This approaches Anonymus in having mar- 

ginal eyes and a sub-central mouth. Like this genus too it has a median indentation of the 

anterior margin, whilst the structure of its penis approaches that of the latter more closely 

than that of other Cotylea. On the other hand the possession of tentacles, a single penis 

and uterine vesicles, ally it rather to the higher Cotylea, such as the Pseudoceridae and Eury- 

leptidae, whilst the extreme folding of the margin, the wide separation of the small tentacles 

and the backward position of the genital apertures serve to distinguish it sharply from all 

its allies. 

The marginal tentacles of Pericelis are of particular interest. They are of a simple and 

primitive character and indicate clearly the manner in which these organs have arisen in the 

Cotylea by the concentration of the marginal eyes on a pair of specialized folds of the margin. 

We can hardly doubt that this concentration has accompanied the acquisition of polarity in 

the organism in its development from a radially symmetrical ancestor. The fact that Anonymus 

has no tentacles, suggests the probability that this remarkable form is far more primitive 

than other Cotylea in that it has never acquired such organs. 

A further development of the tentacles accompanied with the loss of the marginal eyes, 

save of such as have come into connection with the tentacles, gives us the condition found in 

the Pseudoceridae and Euryleptidae. The former family has a more primitive type of pharynx 

than the latter, in which it is tubular ; in the Pseudoceridae it is not unlike that of Anonymus 

or Pericelis.


The Prosthiostomidae resemble the Eiiryleptidae, from which family they are probably 

derived, in possessing a tubular pharynx. They have no marginal tentacles, but the absence 

of these is probably secondary, perhaps a consequence of their elongated form. The structure 

of their male apparatus is very extraordinary, quite unlike that of other Polyclads. 

Lastly, the family Diposthidae described by Woodworth [20] from the barrier reef of 

Australia is probably closely allied to the Eiiryleptidae, but unfortunately no account is given 

of the pharynx. Avihlyceras is regarded by von Plehn [12] as intermediate between the 

Pseudoceridae and Euryleptidae. 

The accompanying tree illustrates the presumed relationships of the Cotylea diagrammatically. 

Pericelis- 

Anonymus- 

Pseudoceridae 

Cotylea 

Amblyceras Dipcsthidae 

Prosthiostomidae 

-Euryleptidae 

The characters of the terminal parts of the female apparatus give strong support to 

the view that the Cotylea constitute a perfectly natural group. In none of them is the 

vagina prolonged backwards beyond the point at which the uteri open into it to form an 

'accessory vesicle' or receptaculum seminis ; its walls are never developed to form a muscular 

'bursa copulatrix,' and the shell-glands always open into it close to the gonopore. Whatever 

specialization of the female apparatus has been developed has occurred either in connection 

with the oviducts themselves as in Oligocladus or with the uteri as in Pericelis and Diposthus. 

[The presence of an accessory vesicle in Enantia, as well as the arrangement of the 

eye-spots and the absence of a sucker form a combination of characters which forbid us to 

refer it, as Benham does [3], to Cotylea. In the possession of a gut anastomosis it does 

not by any means stand alone amongst the Acotylea, witness Leptoplana pardalis, Planocera 

villosa, Eustylochus elUpticus.] 

Cotylea and Acotylea. The Acotylea can be distinguished broadly from the Cotylea 

by the fact that the former as a rule possess an accessory vesicle, a continuation of the vagina 

behind the point where it receives the uterine opening, though this is by no means invariably 

the case, e.g. the genus Hoplopkma. But the most striking and most constant distinguishing 

feature (apart from the sucker) of the two divisions is afforded by the tentacles, when they are 

present. Those of the Cotylea have already been dealt with, and are of course universally 

marginal. 

In the Acotylea marginal tentacles never occur; when they are present they lie dorsally 

immediately over the brain. In the Leptoplanidae and I believe in Enantia these tentacles, 

which in the Planoceridae always carry eye-spots, have been lost, the eye-spots connected with 

them have nevertheless been retained, at any rate in most cases. In the Cestoplanidae so far 

as we know there are no traces of tentacles distinguishable (cf the other elongated family.


Prosthiostonium). In speaking of the remarkable Polypostia Bergendal [1] remarks that ' tentacle 

eyes' can scarcely be distinguished. In passing we may notice that like Anonymus, Polypostia 

is provided with a number of male copulatory organs surrounding the female aperture. The 

fact is that some of the hinder pairs are not connected with the sperm-ducts. This is regarded 

by Lang as an indication that the penis in Polyclads is derived from glandular organs, which 

have only a secondary connection with the sperm-ducts. Whilst this is very probably true, 

it is possible that in Polypostia we have a stage in the disappearance of the multiple radially 

arranged penes that appear to be an ancestral character. In this connection reference may 

be made to the paired penes of certain Pseudoceridae. 

are held : 

— 

Origin of Nuchal Tentacles. Of the origin of the tentacles of the Acotylea two views 

(1) 

That adopted by Lang, who, following Chun, brings forward evidence for supposing 

the Polycladida to be derived from a Ctenophore-like ancestor; and homologizes 

the dorsal tentacles of the Planoceroids with the retractile tentacles of certain 

Ctenophores. 

(2) That of Willey [17], who also derives the Polyclads from a radially symmetrical 

Ctenophore-like ancestor. He suggests that the dorsal tentacles of Polyclads 

are homologous with the sensory tentacles found in certain Ctenophores, and 

especially in Ctenoplana. 

I here have to put forward a third suggestion, which differs completely from either of the 

preceding. Without questioning the probability of the origin of the Polyclads from a radial 

ancestral form, or the possibility of that form being also allied to a form ancestral to the 

Ctenophores, and avoiding any discussion as to the axial relationship of two groups, I 

consider that the tentacles of the Polyclads, whether marginal or nuchal, 

(1) are a structure peculiar to the group; 

(2) that they originated as marginal organs in connection with the eye-spots, somewhat 

in the way I have suggested above 

(3) that in the Cotylea they still retain this condition 

(4) that in the bulk of the Acotylea they have shifted back from the margin and 

come to lie dorsally. 

This theory offers a more satisfactory explanation of the relationship of the Acotylea to 

the Cotylea than is possible on either of the two first. For, if we adopt either of these, 

we must suppose that the Cotylea are descended from forms which have lost all traces of 

the nuchal tentacles, and have in most cases acquired marginal tentacles. Now the Lepto- 

planidae have lost the dorsal or nuchal tentacles but have in almost every species retained 

evidence of their existence in the tentacle eye groups, whilst none of them have developed 

marginal tentacles, although some of them, e.g. Discocelis, have retained marginal eyes. On 

the other hand no Cotylean species ever exhibits any trace of a nuchal tentacle eye group. 

On my theory there is no reason to regard the Cotylea as less primitive than the 

Acotylea; in fact the balance of evidence distinctly inclines to the opposite view. If we 

leave out of account the elongated, obviously highly specialized forms in either group, i.e. the 

Prosthiostomidae and Cestoplanidae, the Cotylea present far greater uniformity and less com- 

plexity of organization of the genital apparatus than we find in the Acotylea ; whilst most 

; 

;


of the special features of the gut-branches of the Pseudoceridae (viz. dorsal diverticula of 

Thysanozoon, marginal pores of Yungia) are paralleled in the Planoceroids and in Polyporus. 

Starting from a hypothetical, primitive, non-tentaculate form such as Anonymus, there is 

no difficult}' in deriving both the Cotylea and Acotylea from it, if we admit that the tentacles 

in the two groups are homologous. There is no difficulty in supposing the margin of the 

body to have coalesced in front of the tentacles, and these latter to have moved back 

carrying their eyes with them, and come into connection with the dorsi-ventral muscles. As 

will be seen, this theory accounts readily for the presence of eye-spots in connection with 

nuchal tentacles. 

There is a possibility that some of the more primitive Acotylea may be directly descended 

from forms that have never developed tentacles, but evidence on this point is lacking. On 

the whole I think that the balance of evidence inclines strongly to the view I have here 

advanced, which has the advantage of being better correlated with what is known of the 

anatomy of the groups 

Natural History Notes. I append some interesting notes given me by Mr Gardiner: 

" All the forms were preserved with HgCL ; 

but, however much they may be expanded, 

all contract when the corrosive sublimate solution is poured on them, hot or cold. Anaesthe- 

tization by cocaine was useless, for, without keeping the animal quiet and expanded, it 

caused the excretion of a large quantity of mucus and this prevented the fixing fluid from 

getting at the tissues. Usually in cocaine, too, the animal began to rot and break up before 

it was sufficiently quiet to be killed. Chloral hydrate seemed to have little effect and alcohol 

did not begin to act for some hours, and as soon as the animal became quiet it began 

to secrete mucus, a fatal difficulty. The best way to preserve would be, I believe, to drop 

specimens straight into a bottle of HgCla on the reef itself or into strong—at least 10 per 

cent.— formaline, removing after 15—30 seconds into concentrated corrosive. 

" It is almost impossible to get the Thysanozoons off the rocks, as they break up readily. 

With all forms the only really effective way is to tease them and make them project them- 

selves into glass tubes. A large Thysanozoon (?) secreted an enormous amount of mucus, and 

broke up rapidly into separate pieces ; its mucus collected a large amount of dirt, and killed 

the other animals in the bottle. It also extruded a quantity of faecal matter. The smooth- 

skinned forms do not secrete so much mucus, but really each form requires to be placed at 

once and killed in a separate vessel. 

" I carefully examined for the food of these Platyhelminths and found them browsing on 

Tunicate colonies and sponges, whilst others had been eaten by them under the same stones. 

Weed was not generally touched, but dead animal-matter laid down under stones proved an 

attractive bait. They do not browse on Gylicia, Goenopsammia, nor any of the corals whose 

normal habitat is their own. Hydrozoa and Actinia too are not touched. Often at Hulule 

I turned over rocks which had Tunicate sponges and colonies of hydroids; but it was only 

the Tunicates that were generally attacked, the sponges being rarely touched. 

"The Turbellaria live principally under stones and rock, especially where the latter is 

lying freely upon the reef Sand is deleterious, and, if much of it is present, no forms will 

be found. When a rock is overturned the Planarians hurry off in all directions, some over 

' I am aware that the embryological method lends no support so far as I know to this view, but neither does it 

make for either of the alternatives. 

—


its edge, but the majority into any holes on its surface. If however the hand is placed 

over one, it will remain contented for some time in any damp spot and will not come into 

the light. That the latter in any strength is what the animals object to is clear, as in 

glass vessels they always get to the side away from it and hide under the lee of any stones 

which may be placed in the water. 

" It is noteworthy that the Turbellaria do not generally occur on reefs or reef-patches 

within the lagoons, nor indeed where there is not an ample change of water. The animals 

are never found on growing coral, perhaps on account of the light. 

"The colours are in no sense protective, nor do I think they can be warning. I have 

never seen, either on the reef or in basins, any free-living animals attack them, though 

I have expressly placed various species together in glass beakers for this purpose. 

"I would suggest that the pigment is respiratory. It is, I believe, quite true for each 

species. Under any rock mass it is common to find many Tunicate colonies of one species, 

and one species only. This may be white, red, pink, blue, or purple, yet the Turbellaria 

did not appear to me to differ in colour under different masses of rocks." 

In conclusion, my thanks are due to Mr Stanley Gardiner for giving me the opportunity of 

undertaking this work, and to Dr Gamble for much assistance with regard to literature. To 

both these gentlemen I am indebted for useful advice and suggestions. I have also to thank 

Professor Hickson, both for penuission to carry out ray examination of this collection in the 

Zoological Laboratory at Owens College and for the kind interest he has displayed in the work. 

III. LITERATURE. 

1. Benham. Treatise on Zoology, Pt. IV. 1901. 

2. Bergendal. Kongl. Fysiogr. Sallskapet ; Lund Handlingar Ny Foljd. 1892—93, Bd. 4. 

3. Rev. Biol. Nord France, v. pp. 257—366. 

4. CoLLiNGWOOD. Trails. Linn. Sac. Lond. ii. (Zool.) i. 1875. 

5. Gamble. Q.J. M.S. xxxiv. p. 433 (1893). 

6. Graff, v. Zeitschr. wiss. Zool. LV. 1893, p. 189. 

7. Mitth. naturwiss. Ver. filr Steiermark, Jahr 1889. 

8. IJIMA. Zeitschr. wiss. Zool. xi. (1884), p. 359. 

9. Lang. Naples Monogr. xi. 1884. 

10. Plehn, von. Jena Zeitschr. xxx. p. 137, T. viii—xiii. 

11. Ergehn. Plankt.-Exp. Heft i. (1896). 

12. Jena Zeitschr. xxxi. p. 90, T. v. (1898). 

13. Zool. Jahr. Syst. xii. p. 448—452, 2 figs. (1899). 

14. Stummek-Traunfels, von. Zeitschr. wiss. Zool. Lx. p. 688, T. xxxv—xxxviii. 

15. Verrill. Trans. Connect. Acad. viii. pp. 459—520. 

16. Wheeler. Am. Journ. Morph. ix. p. 167 (1894). 

17. WiLLEY. Q.J. M.S. xxxix. pp. 323—342. 

18. Q. J. M. S. XL pp. 293—205. 

19. WOODWORTH. Bull. Mus. Harvard, xXL p. 1 (1891). 

20. Bull. Mas. Harvard, xxxn. pp. 63—67 (1897).

Fauna and Geoqraphy Maldives and Laccadives. 

Laidlaw - Turbellaria. 

Plate XIV 

^ Hîlson, Ca mbi-tdi^ e 

.


EXPLANATION OF PLATES. 

(? = male aperture. pe 

2 = female aperture. pi 

a.d. = accessory duct. pr 

a.m. = antrum masculinum. p.r. 

a.v. = accessory vesicle. p.m. 

b.c. = bursa copulatrix. p.s. 

c = chitinous stylet. r 

c.d. — common duct. r.m. 

c.e. = columnar epithelium. rh 

c.h. = chitinous hooks. s 

c.r. = chitinous ring. s.ff. 

c.s. = chitinous spines. s.p. 

d = gut-diverticulum (of Planocera armata). u 

d.e. = ductus ejaculatorius. u.g. 

e.t. = tentacle-eyes. u.v. 

h = hyaline layer. va 

hy = hyaline secretory bodies. v.s. 

n = nervous tissue ves.d. 

o.s. = outer sheath. y 

p = pigment. x 

p.g. = pigment granules. 

p.m,. = pigment mass. 

Fig. 1. Planocera lanyii n. sp. 

PLATE XIV. 

; penis. 

: fold of lining wall of the penis. 

; prostate 

gland. 

: pseudorhabdites. 

; penis 

intrinsic muscles of the penis. 

sheath. 

: rod-like bodies or bacteria. 

retractor muscles. 

: rhabdites. 

: secretion. 

: shell-glands 

= dark secretory bodies. 

: uterus wall. 

= glands on the uterus. 

= uterine vesicle. 

= vagina. 

= vesicula seminalis. 

= duct from the uterine vesicle. 

= cells resembling yolk-glands. 

= 'plug-like' tissue at the tip of a dorsal 

papilla. 

Fig. 2. Prosthiostomum cooperi n. sp. Anterior third of adult specimen. 

Fig. 3. Pseudoceros tigrinus n. sp. 

Fig. 4. Pseudoceros gardineri n. sp. Tentacles, eye-spots of the dorsal surface and part of the 

anterior margin. 

Fig. 5. Pseudoceros punctatus n. sp. for comparison with the preceding species. 

Fig. 6. Pericelis byerleyana n. sp. 

Fig. 7. Thysanozoon plehni n. sp. 

Fig. 8. Prosthiostomum elegans n. sp. 

Fig. 9. Leptoplana pardalis n. sp. 

G. 40

312 F. F. LAIDLAW : THE 

MARINE TURBELLARIA. 

PLATE XV. 

Fig. 10. Planocera armata. Transverse section across one of the gut branches, showing on its dorsal 

side a pouch-like diverticulum, x 500. 

Fig. 11. Longitudinal median section through the genital apparatus of the same, reconstructed 

from transverse sections. Somewhat diagrammatic, x 60. 

Fig. 12. Transverse section across the penis of the same at the level of the chitinous hooks, x 110. 

Fig. 13. Transverse section of the penis of Planocera langi at the level of the pair of large folds 

projecting into the lumen. The section also passes through outer sheath and the 'recep- 

taculum seminis.' 

Fig. 14. Transverse section through the penis of Leptoplana pardalis. 

Fig. 15. Longitudinal section through part of the oviduct of Pericelis hyerleyana, passing also 

through one of the accessory uterine vesicles. 

Fig. 16. Section passing transversely through part of the oviduct of the same. 

Fig. 17. Transverse section through a tentacle of the same showing the very regular columnar 

arrangement of the epithelium on the dorsal surface'. 

Fig. 18. Section through the penis of a specimen of Pseudoceros gamhlei. 

Fig. 19. Section through a dorsal papilla of Thysanozoon plehni showing the absence of any gut 

diverticulum ; and the curious ' plug-like' mass of tissue (.r) at the tip of the papilla. 

Fig. 20. Section through the accessory vesicles of the penis and part of the antrum masculinum 

of Prosthiostomum elegans. 

1 Indicated by the lettering c.e.

Fauna and Geography Maldives and Laccadives. 

. A^- 

fiff d 5'"'^ CS 

Plate XV.

THE MALDIVE AND LACCADIVE GKOUPS, WITH NOTES ON OTHER 

CORAL FORMATIONS IN THE INDIAN OCEAN (continued). 

By J. Stanley Gardiner, M.A., Felloiv of Gonville and Cams College, 

and late Balfour Student of the University of Cambridge. 

(With Plates XVI. and XVII. and Text-Figs. 74 and 75.) 

CONTENTS. 

Appendix A. Special Observations and Wobk relating to the Formation and Growth 

OP Coral Reefs. 

Section I. The Seaward Slopes op Atoll Keeps ........ 314 

Topography—Reef-edge (Fissures, Organisms, etc.)— 10 to 15 Fathoms (Corals and 

Lithothamnion)— 30 Fathoms (Form of Growth and Genera of Corals, Polytrerna)—Summary. 

Section II. The Formation of Lagoons .......... 317 

Addu Lagoon (off Huludu, Lagoon Flat, Coral Growth, Character of Bottom, 

Soundings, Shoaling, Physical Conditions, Causes of filling in. Conclusions) 

General Growth in Size—Circulation of the Water—Solution—Analyses of 

Deposits—Conclusions. 

Section III. The Bathymetrical Limits op Coral Reef Builders .... 323 

Dredging—Table of Coral Genera and Depths—Corals between 20 and 40 Fathoms 

— Heliopora and Mille.pora— Polytrema— Algae Diaseris—Conclusions. 

Section IV. The Rate op Growth op Corals and Reeps ...... 327 

The Problem— Literature—Artificial Canals in the Maldives—Coral Growth and 

Physical Conditions of Hulule Canal—Table of Growths of Corals— Rate of 

Growth of Reefs—Conclusions. 

40—2 

— 

—

314 J. STANLEY GARDINER. 

Section V. The Action of Boring and Sand-feeding Organisms 333 

I. General— Importance for Solution— Action and Effects of Organisms—Deposits 

of Coral Muds and Sands— II. Boring Organisms— Sponges and Algae 

Lithodomus—Sipunculoidea—Polychaeta (great Importance of, Distribution, 

Note by Prof. Wlntosh)—Lithotrya—Other Forms—III. Sand-feeding Or- 

ganisms—General—Holothurians (Distribution, Holothuria maculata, Observa- 

tions on Stichopus chloronotus and Holothuria atra)—Echinids—Abundance of 

Ftychodera— SipuMculns— Polychaeta. 

Section VI. Beach Sandstone ............ 342 

Conditions of Formation—Protected Beaches—Presence of Silica or Organic Matter 

— Constitution—Mode of Occurrence—Development—Undermining—Terraces 

Erosion of Land— Justifiable Deductions. 

(To be continued.) 

APPENDIX A. 

Section I. The Seaward Slopes of Atoll Reefs. 

I HAVE already repeatedly referred to the subject-matter of this Section in the previous 

Chapters of this Report (pp. 38—44 and 177). I have also therein stated that the reef is 

growing up everywhere outside the atolls (p. 49) without really attempting to show or prove 

that such is the case—to a certain extent assuming the upgrowth to be a matter beyond 

dispute. I have done so for two reasons, (1) to simplify the subject-matter in the previous 

chapters, and (2) because I felt that without a special, more detailed, yet somewhat 

generalised account of the whole seaward slope it would be impossible to satisfactorily show 

the evidence on which the above deduction was based. In the following pages I have 

attempted such a description, but I freely recognise that our investigations of the seaward 

slope in the Maldives were scarcely sufficiently complete to really warrant my doing so. 

The outer or seaward slope of any bank in the Maldives opposite its encircling surface 

reefs is usually covered with a dense growth of corals and other organisms down to the 

depth at which the steep commences. The edge of the reef, although broken up by fissures 

extending into it for some distance, is usually fairly well-defined. Beyond it the seaward 

slope, as deep as the eye can see, i.e. to about 15 fathoms, is generally much broken up 

by masses and buttresses of the rock, the latter extending out at right angles from the reef, 

as well as by large colonies of corals. At least the latter evidently continue further out 

to 25 or 30 fethoms, the lead down to these depths often resting for a moment and then 

dropping off again for an additional 2 or 3 fathoms. The bottom, however, so far as the 

actual masses of the reef rock are concerned, actually becomes more level with each ad- 

ditional fathom of depth, until beyond 30 fathoms the reef-platform in the slope of its 

foundation rock is almost or quite level. 

— 

PAGE

SEAWARD SLOPES. 

The reef edge and the area immediately outside it are extremely difficult and dangerous 

to examine on account of the rollei-s, which, always breaking to some extent even in dead 

calm weather, are followed by a strong outrush of water. The surface of the rock in this 

position is fairly smooth, being generally covered with incrusting Lithotharnnion or with great 

colonies of a yellow Zoanthid Actinian. On those masses and buttresses, that are exposed 

in the backwash preceding each breaker, the upper surface of the rock is generally pitted, 

a little green weed often growing in its hollows. The sides of the masses commonly overhang, 

and are usually covered with LiUiotJiamnion. Down to 5 fathoms the corals are of stunted 

growth and are only found in such hollows as are more or less protected from the rushes 

of water, which follow each breaker. The bottoms of the channels between the ridges usually 

appear white in colour, as if silted with small pebbles or coarse sand. In addition large 

coral masses may occasionally be distinguished. The filling up then of the fissures between 

the buttresses and masses would naturally to some extent follow their upward growth. 

The dominant organisms in the formation of the masses of rock between the surface 

and 5 fathoms are undoubtedly those of the genus Lithothamnion. Unfortunately we know 

little or nothing about the mode or rate of growth of these plants, but the rate can scarcely 

be nearly as rapid as that of corals. The latter organisms may then perhaps be of far 

greater importance than the number or bulk of their living colonies in this area would at 

first sight lead anyone to suppose. That the reef is growing up admits of no doubt. In 

the few fragments of rock, I obtained between 1 and 5 fathoms, the species of Lithothamnion 

show a definite, though perchance somewhat irregular, layered growth. Boring organisms, etc. 

in them are rare, and neither they nor the corals of the area show any rotting of any 

sort. In Fiji I saw a few masses of rock broken off the edges of reefs in hurricanes and 

hurled back on to the reef flats, i.e. true negroheads. In the Maldives on the other hand, 

such negroheads do not exist on those reefs which fringe the open ocean. Moreover I never 

saw any sign whatever of the breaking off of definite masses of rock, either large or small, 

to seaward of any ordinary reef, nor for at least a dozen yards within its edge'. The absence, 

too, from the seaward shores of islands of fragments of coral or recent rock except such 

as grow or form on the reef flats proves of how little importance in the Maldives the de- 

structive action, even of heavy gales, is on the edges of the reefs. 

The next zone, 5 to 10 fathoms, shows a transition to the third, 10 to 1.5 fathoms. 

In the latter buttresses and masses are scarcely recognisable as such. No overhanging rocks 

with definite charmels or fissures between are found. There is, nevertheless, a tendency for 

lines of low elevations— in section transverse to the slope appearing as rounded undulations 

— to run out at right angles to the reef behind, but even these are not always very distinct. 

Occasionally hollows, 2 fathoms or more deep, with sandy bottoms are seen, generally con- 

siderably overhung by growing corals. Such pools are, however, rare on those sides of the 

reefs, which are fully exposed to the ocean, but the whole of this area is sometimes 

represented by a succession of them. This is notably the condition, where the slope is 

protected from the full force of the ocean, such as against channels between atolls and 

against the central basin of the gi'oup, the Great Maldive Sea. 

1 In this connection I do not refer to tUe breakinfj off of surface, but by far the greater part is undoubtedly carried out 

branches of corals, etc. by the undercurrent on the reef slope, over the edye of the steep, thus extending the whole reef 

•which follows each breaker (see p. 24). Any loose material further and further seaward, 

may assist to fill in the hollows and crevices on the reef 

315


Even where the reef lies against the open sea, it is freely studded between 10 and 15 

fathoms with species of nearly all the massive genera of corals, forming rounded colonies 

up to a few feet in diameter, often dead in the centre. The branching genera are not 

perhaps as numerous ; where they occur the facies of their growth is that of low spreading 

thickets with very occasionally a larger tree of some vigorously growing species of Madrepora 

or Pocillopora, casting defiance at all law and reaching to within 3 or 4 fathoms of the 

surface. The reef in the above-mentioned, protected situations in many places appears to 

be almost completely covered with growing corals, which interlock, strive and struggle with 

one another in the same way and quite as much as, or even more than, on the most 

luxuriant lagoon reef in the whole groups 

Lithoth amnion may appear almost non-existent in a surface view, but on all outer slopes 

at this depth (10 to 15 fathoms), wherever a bare space is to be seen,—not a pit overhung 

by corals—there at the least a thin coating of the incrusting species of this organism will 

certainly be found. Sometimes the forms of the genus seem to grow into rounded or nodular 

masses, 2 to 3 feet or more in diameter, and standing up on the basal rock, but all such 

that I have examined have a basis—a central nodule—formed by some coral or other 

organism, which they have overgrown and perchance killed. Even in small masses of less 

than a foot in diameter a thickness for the nullipore of 2 to 3 inches is not unusual. In 

reality nearly everywhere these calcareous plants are growing at the bases of the corals. 

The coral colonies are ordinarily dominant, but, when one becomes sickly, the species of 

Lithothamnion soon claim sway, and extinguish it. In addition small, coarsely or finely 

branching growths of the same genus are also found, but these facies are of little importance 

as reef builders. Indeed the main significance of Lithothamnion lies in the peculiar mode 

of growth of its incrusting species. Whatever is reclaimed from the sea by any coral 

organism is secured by these plants, and firmly anchored once for all time to the reef so 

far as the action of the external ocean is concerned. 

Dredging on the outer reefs is such uncertain work even in a steamer—and in addition 

so dangerous in a sailing vessel as to be almost impossible—that we could not afford the 

time necessary to make a proper study of the organisms below the depth of 15 fathoms, 

above which we could see what we were doing. Such organisms, as we secured from it, 

were only obtained while attempting to ascertain its general topography, of which I have 

already given a sufficiently full account. 

' It is quite impossible to collect and investigate an area 

such as this without extremely calm weather, tackle of the 

strongest description, and most important a steamship. 

A Priestman's grab, such as can be used by hand, seldom 

secures a coral of any massive genus and only broken stems 

of branching genera. The smaller massive colonies spread 

outwards at their attached bases, and the grab cannot be 

fixed on them. Moreover there is always some roll of the 

sea even in the calmest weather, and, when a coral mass of 

even 8 or 10 inches in breadth is securely fixed in the grab, a 

whaleboat or small launch will be pulled under the approach- 

ing waves before it be released. 

The genera of the corals from to 5 fathoms, forming 

only small colonies and the zone being difficult to examine, 

could not be accurately determined. Finely branching species 

of Pocillopora were, however, evidently by far the most 

abundant. 

The following is a complete list of coral genera observed 

from 5 to 1.5 fathoms outside the reefs, the first 10 arranged 

in the order of their importance as builders in this position 

1. 

2. 

:

LAGOON FORMATION, 317 

The gradual passage of the outer slope of any reef into a fairly smooth platform points 

to the fact that the foundations of the existing, encircling surface reefs of the atolls are 

really laid at some depth below 25 fathoms. Many of the same genera of branching corals 

(Madreporaria)— perhaps even the same species—occur at 30 fathoms as are found at 10 to 

15 fathoms, but their form of growth is quite different. At the lesser depth the coralla 

are dense and heavy, the branches relatively thick and massive, and the colonies of large 

size compared with the sickly growths obtained at the greater depth. The genera of corals 

found at 15 fathoms are also mainly those that occur on the reefs, but at 30 fathoms 

additional genera make their appearance. Leaving genera of simple or of semi-simple species 

out of account, Dendrophyllia, Goniopora and Alveopora all grow in great luxuriance. Our 

swabs came up nearly every time thickly crowded with the branches of Dendrophyllia ramea, 

and many masses and fragments of the others were secured. Of even greater importance 

off Addu atoll was the Alcyonarian Heliopora coerulea, which was secured in each of six 

dredgings from 25 to 45 fathoms. Its facies were staghorn, lamellate and almost massive, 

and the quantity secured would show that large areas of the bottom must be covered by 

its colonies. In two of the dredgings pieces of the Hydrocoralline Millepora were obtained, 

and the same coral was also found incrusting a fragment of dead Anacropora. Ualimeda 

is abundant, and Lithothamnion of incrusting or low branching facies also occurs. The position 

of the latter, nevertheless, is largely taken by incrustations of white Polytrema, to the 

importance of which Chapman' has lately drawn attention. Dead blocks of coral or other 

rock are not infrequent, and are generally completely or in great part covered by this 

organism. Of other animals, of little or no importance in building up reefs, it is only necessary 

to remark that this area is essentially the home of Gorgonians and Crinoids, while Alcyona- 

ceans are very common. No deposit of sand or small rubble, be it observed, is ever found 

at these depths. 

The most striking character of the whole of the seaward slope to the commencement 

of the êep, i.e. the reef platform, off the atolls of the Maldive group, is the almost complete 

clothing of the bottom with organisms of various kinds. The bare rock is practically nowhere 

exposed to the sea, so that the possibility of the latter eroding or dissolving away the rock 

must be over the whole outer slope largely discounted. All the corals and calcareous organisms, 

obtained from the reef platform, markedly differ from those off surface reefs or from lagoons, 

in that boring organisms are almost completely absent. Indeed all indications of change 

point to the active gi'owth upwards of the whole bottom in this region of the seaward slope 

rather than to the possibility of its being by any means washing away. 

Section II. The Formation of Lagoons. 

The matter dealt with in this Section has already been to some extent considered in 

the preceding Chapters, but the subject is of wide interest in view of the various theories 

that have been propounded to account for the formation of coral atolls. There are also a 

few points to which attention should be more particularly drawn in the conditions at the 

present time of some of the atoll lagoons in the Maldive group. 

Addu atoll''', firstly, is of interest in that its lagoon is filling up rather than increasing 

Jour. Linn. Soc. vol. xxviii. pp. I and 161. As it is, I am indebted to Mr Forster Cooper and Capt. Molony 

- The work in this atoll was carried on in the intervals of for all tlie soundings and most of the information about the 

fever, and was not nearly as complete as I could have desired. lagoon.


in size and extent. There is between the land, wherever it exists, and the lagoon basin a 

flat of some sort, covered with dark, muddy sand, gradually getting whiter further out from 

the land. The inner part of this is to some extent exposed at low tide, and off Midu in 

the north-east corner the exposed area attains a breadth at springs of about 700 yards. 

Further at ordinary low tide neither this village nor Huludu can be approached even in a 

small dinghey within several hundred yards on account of this platform. The outward edge 

of the flat against the lagoon is quite well-defined—being covered with growing corals, 

Lohophytum and other organisms—and lies at a distance of about \\ miles from the land 

its depth in this part is such that it can be conveniently waded at low tide, i.e. about 

4 feet. The high water mark is about 3 feet up the beach, and, the tide being about 

4 feet, there is thus in this comer a great platform, extending out for 1^ miles from the 

^ffsc^t 

Suek 

'"^'tS'-'// 

'/Iffuludu 

Fig. 74. Addu Atoll. The map is based on the Admiralty Chart, altered iu accordance with the observations of the 

Expedition. Mr Forster Cooper's soundings alone are marked. Scale 2 miles to 1 inch. [For changes compare 

the Admiralty Chart on p. 150.) 

land, with a slope in this distance of about 5 feet. This, however, is not all. Absolutely 

in the corner, not stretching for any distance either to the west or south, is a strip of 

deeper water averaging nearly 300 yards in breadth, separated by a second reef from the 

lagoon. This outer reef varies from 10 to 60 yards in breadth, and is rather patchy and 

ill-consolidated with no definite flat. It is built up almost entirely of corals, and approaches 

the surface so closely that it can only be crossed at low tide through certain definite 

channels. The false velu, as the inner lake or basin may be termed, has a general depth 

of about 5 fathoms, against which the enclosing reef forms a sloping wall. Towards the 

;

LAGOON FORMATION, 319 

atoll lagoon the slope of this same reef is nearly perpendicular, the depth immediately attained 

being generally greater than 8 fathoms, whence the bottom slopes to over 20 fathoms in 

about 150 yards. 

The lagoon flat against the land in Addu atoll presents elsewhere more or less the 

same characters, but the deep inner channel is not found. Its edge against the lagoon is 

well-defined, precipitous, covered with coral and at about the low tide level. Within it there 

may be a slight hollowing out for 2 or 3 feet, but this shallow basin partakes rather of 

the nature of a boat channel and is in no way comparable to a velu. An analogy to the 

north-eastern velu is only found in the north-west horn, where a portion of the bay has 

almost been cut off from the atoll lagoon by the growth of coral knolls. The upper part 

near its head is a fairly clear basin, covered on the bottom with muddy sand. Towards 

its mouth, where it opens into the lagoon, these coral 

per]5endicularly— perhaps overhanging at the top—from 

heads stud the 

10 fathoms or 

whole surface, 

even deeper. 

arising 

Many 

of the knolls have grown together, so that a passage to the head of the bay is at the 

present time difficult for a vessel of any size, if not impossible. A basin or false velu is 

thus being formed by the upgrowth of a reef within the lagoon. Without having seen the 

growth of shoals in this horn it would have been difficult or impossible to diagnose the 

formation of the outer lagoon reef off the other (north-east) horn of the atoll. The analogy 

is, however, so close that there can be no reasonable doubt, but that it arose in the same way. 

The coral growth, taken as a whole, in Addu lagoon is most extraordinary, and in vigour 

quite surpasses anything in my experience elsewhere either in the Maldives or in the Pacific 

Ocean. On all sides of the lagoon the reefs appear to have grown out into its basin, and 

fresh patches of coral are everywhere off them being built up towards the surface. The 

reef patch, charted by Moresby in 1836 to the north of the south-east passage, has become 

joined to the reef, and the horns on both sides of this same channel have grown further 

into the lagoon. Mr Forster Cooper in addition found a shoal patch with 6 fathoms im- 

mediately where the same passage embouches into the lagoon. Otherwise in the southern 

channels I could see no change either in depth or breadth, but the natives report that the 

two northern ones are now impassable for their vessels, while they seem to have been 

regularly used when Moresby surveyed the atoll. 

The bottom of the lagoon was found by my companion, Mr Forster Cooper, to be covered 

with rubble and sand, one small patch of mud only existing at 27 fathoms to the head 

of the north-east horn. The rubble consisted of coral masses and shells on which were 

growing large trees of Dendropli i/lli.a, colonies of Madrepora and Pocillofora, Polytrema, 

Pohjzoa, great masses of Alcyonacea, Halimeda and sponges. The sand consisted merely of 

finer ftugments of coral and other organisms, Halimeda remains and a few fi:-ee bottom-living 

Foraminifera. Sedentary and indeed all other organisms were on this class of bottom singularly 

scarce. 

Mr Forster Cooper investigated with soundings all parts of the lagoon, paying more 

particular attention to those, which were charted as having more than 30 fathoms of water. 

Making every allowance for the possibility that the soundings may have been too low—of 

which, nevertheless, there was no indication— the greatest depth obtained by my companion 

was 32 fathoms, where 36 fathoms ought to have been found. Where 39 fathoms are charted, 

only 31 fathoms were obtained. Isolated soundings may mean nothing on account of difficulty 

of fixation— in this atoll intensified by considerable changes in the land. Eliminating all but 

G. 41

320 J. STANLEY GARDINEK. 

the most careful observations—many having been taken when dredging—23 are left, all of 

which show a decrease in depth of from 1 to 8 fathoms, the general reduction being 2 or 3 

fathoms. 

It will be clear from the above remarks that Addu atoll differs from all others in our 

group in the fact that it shows a decrease in depth in its lagoon. Minutely examining all 

the factors as given above and comparing as far as possible with the chart, I estimate 

that in the 65 years between Moresby's visit and my own there has been at the least 

a decrease in depth of 2 fathoms over the whole area of the lagoon proper, i.e. about 

15 square miles. The whole lagoon is about 22 square miles, and there must be taken 

into account the inward extension of the lagoon reefs, a far more rapid increase. To suppose 

therefore, for the 60 odd years since the survey, a deposit or filling in by coral growth of 

2J inches a year over an area of 22 square miles does not seem to me to be excessive. 

To account for this decrease, it should in the first place be pointed out that Addu 

atoll is markedly different in its topography to all the other banks of the group. From 

my corrected chart I estimate that five-sevenths of its circumference are protected by land. 

There are only fom- narrow passages—two extremely small—with an average dej)th over their 

whole sections of probably less than 10 fathoms. There is thus not likely to be much 

circulation of water in the deeper parts of the lagoon. The prevailing winds and cuiTents 

are east and west ; from the latitude being almost that of the equator it is obvious that 

they vary but little in different seasons of the year, inclining only somewhat to north-east 

and south-west. Further the ordinary currents and winds never can have the same force 

as in the more northern atolls, and hurricanes do not occur so far north or south. By 

a glance at the chart, it will be at once apparent that in no case can the usual currents 

or winds affect the lagoon, owing to the positions of the passages and the protection afforded 

by the land. As important factors in Addu, which they certainly are in other atolls, they 

may accordingly be neglected. The tidal rise and fall is stated to be 4 feet—on the lagoon 

beaches certain measurements I made averaged 3 feet 8 inches, but it does not follow that 

the rise within the lagoon would be as great as on the seaward sides of the islands—which 

is certainly less than in any other part of the group. Lastly, the encircling reef of Addu 

averages more in breadth than that of any other Maldivan atoll, and the tidal water in 

crossing it would be more likely to be saturated with lime before ever it got to the lagoon, 

so that there could be by its means little solution. 

The chief agent in this filling in of the lagoon of Addu atoll is coral growth. Its 

luxuriance is quite without parallel in any of the described regions of the world, similar in 

the size and closed character of the area. I have unfortunately no definite observations, 

which serve to explain its cause. The water of the lagoon, owing to its protection from -svinds 

and currents, would naturally be considerably clearer than in most basins. The periphery, 

over which the surface fauna might be supposed to pass to the interior of the lagoon, is 

only 8 miles, but I would emphasise the fact that all those kinds of corals that form the 

reefs feed rather by their commensal algae. With regard to this it is probable that, from 

the decaying matter of the lagoon flats and land, an especially abundant supply of carbonic 

acid gas is provided. This would seem at first sight to be opposed to my argument that 

the tidal water would be saturated with lime before ever it reached the lagoon. All the 

carbonic dioxide would, I conceive, on account of the abundant growth of corals be utilised 

by them, but the sea-water has a solvent action on calcium carbonate, independent of the

LAGOON FORMATION. • 

321 

presence or absence of this gas. The greater average and the lesser range of the temperature 

of the sea-water as compared with more northern and southern atolls (comp. Chagos 

Archipelago) would probably be an additional factor favourable to coral growth in this region. 

Lastly, destructive organisms of all kinds are relatively scarce in this lagoon. The larger 

boring animals are rarely found in the coral skeletons. Indeed in our record of dredgings 

I do not see a single form recorded, although in contrast to most atolls much rubble was 

obtained. This is further confirmed by a few corals, which we brought home from the area, 

in some pieces even the minuter boring sponges being absent. Holothurians and Sipunculids, 

the two most important sand-triturating forms in such an area, were singularly scarce both 

on the reefs and in the lagoon, so that there would be in the sea-water a lesser quantity 

of finely-suspended matter to be removed by the outgoing cuiTents. 

On the whole Addu undoubtedly owes the shoaling of its lagoon rather to want of 

solution than to the luxuriant growth of organisms, but, the greater the latter, the smaller 

are the solvent surfaces on which the sea-water can act. That Addu really had a considerably 

greater depth when Moresby's survey was made, and possibly still greater at a previous period, 

admits of no doubt. The reason of the relatively sudden filling in of its lagoon can only, 

I think, be ascribed to increase of land and decrease of depth in the passages, both tending 

to hinder the free circulation of the sea-water. Against this must be set the possible decrease 

of the area, from which sediment is supplied for filling in the lagoon. It appears to me 

doubtful, though, whether this would actually be the case or whether the effective source 

of sediment would not rather be enlarged with increase of land. The factor, however, is of 

small importance compared to the prevention of circulation in the water and hence of solution. 

Finally, I may venture to remark that the physical conditions at this latitude are such 

that it is not unreasonable to suppose that the encircling reef of Addu atoll might have 

grown up from a greater depth than would be possible in the more northern parts of the 

Maldive group. The area of the shoal being small, the rim too might have been perfect 

from the first, and the lagoon would consequently * have had a greater depth. In any case 

there is nothing in the existing conditions against the supposition that the lagoon may have 

been at one time greatly deepened by solution, while at present it is decidedly being filled 

in by coral growth and deposition of sediment. 

Everywhere else in the Maldives such change as there has been in the lagoons has 

been one rather of loss than gain. In the first place the soundings show in the larger 

atolls an increase rather than a decrease. In dredging, a hard smooth bottom, free fi'om 

rubble, was constantly found. The lagoon shoals generally fall almost perpendicularly to 20 

and sometimes even to 30 fathoms, depths at which they could scarcely have originated in 

a lagoon. Great falls of rock from their sides are not infrequently found, while the amount 

of rubble around them is relatively small and forms but a very narrow circle. Boring 

organisms— so scarce in Addu atoll—are present in extraordinary abundance in other lagoons, 

and of great importance in destroying corals. The presence of much dead and decaying coral 

would perhaps provide an abundant supply of carbonic acid gas for solution on the lagoon 

floor, a position where much could not be absorbed by the corals. 

The circulation of water in all the other atolls of the group is much greater than at 

Addu owing to their relatively much more extended, peripheral reefs, to which must be added 

the lesser percentage of their surface covered with land. The passages into their lagoons 

are generally both far more numerous and deeper, consequently producing a gi-eater amount 

41—2


of change in the sea-water. The currents of the two monsoons are important as well as 

the tidal current over the whole bank. With the banks close together and having deep 

passages these largely pass directly through the atoll basins. They thus sweep out small 

particles in suspension as well as frequently renew the water, so that the total amount of 

lime removed is greatly increased. The want of protection by land is important, for, whereas 

Addu lagoon with a westerly gale was quite calm and the water clear to 10 or 12 fathoms, 

Goifurfehendu and Bodu-faro (N. Mahlos) basins—both as completely enclosed by surface 

reefs—with not heavier winds were so churned up that the bottom was scarcely visible at 

6 fathoms. The sea in rough weather was noticed to be quite milky even some miles off 

Suvadiva, Haddumati and North Male, while immediately off Addu it was comparatively 

clear. Even in calm weather the meshes of our tow-nets tended in passages to get blocked 

up with dead organic matter and fine mud in suspension, showing what enormous effect 

this sweeping out might have with a moderately rough sea. This movement of organic 

matter has another, an indirect effect in the formation of lagoons of infinitely more 

importance than its direct effect, i.e. in driving mud against the living reefs and corals, 

causing the extinction of small coral colonies and larvae, and enormously hampering the 

growth of larger masses. This effect of mud I have already drawn attention to in the 

Pacific. In the Maldives I had abundant opportunity of confirming my observations, and 

I would only here emphasise what I then wrote'. 

Important as the outwash of detritus really is, I cannot for a moment consider that 

it apjjroaches solution in its effects in deepening lagoons after the reefs on a bank have 

assumed the definite atoll condition. On banks such as Suvadiva, Felidu, Kolumadulu and 

Haddumati considerable areas of the bottom must—owing to the perfection of these atoll- 

forms—be affected to an insufficient degree to greatly stir up their deposits, while probably 

the currents and winds would give an amj)le circulation for solution by the sea-water. That 

this is the case is clearly shown by the presence in protected situations of deposits of soft 

mud. Any deposit of the lagoons, however clean it may appear, has always a distinct 

amount of organic matter in the process of decay, this providing carbonic acid gas for the 

solution. The absence generally of deposition of calcium carbonate in dead coral masses in 

the larger lagoons—common in many of the smaller atolls and faro—would go to prove 

that there is no supersaturation by the lime, and hence that there is free circulation of 

the water. 

Some of the muds are being examined by Sir John Murray, and will form the subject 

of a separate report. I however made a series of analyses to ascertain the silica (SiOa) 

in a number of samples'-. The analyses of 14 surface sands and rocks gave an average 

percentage of 047 of silica, while three samples of mud from 40—50 fathoms fi-om Suvadiva 

lagoon gave 2"441, the latter thus having about 50 times as much silica as is found in 

the surface rock. To put the matter in another way—admitting solution—about 50 volumes 

of the sand and rock from the reef and land would have to be dissolved to give the 

amount of silica found in 1 volume of the Suvadiva mud. No doubt some of the excess 

of silica in the latter may be explained by special causes, influencing its formation. Never- 

theless I fail to see that any complete explanation can be afforded that does not take into 

consideration the solvent action of the sea. 

1 Loc. cit. p. 484, et seq. Chemical Laboratory of Gonville and Caius College at my 

2 I am indebted to Mr M. M. Pattison Muir for placing the disposal during the Easter vacation for these analyses, and

DEPTH OF CORAL GROWTH. 323 

In conclusion, it is a fail- deduction that the increase both in depth and extent in the 

lagoons of the Maldive atolls is mainly due to solution, an important additional factor being 

the outwash of fine matter by the tidal and oceanic currents. It is obvious, though, that 

there are two nicely balanced sets of conditions, causing the filling in or increase in size 

of any lagoon. A quantitative estimation of these, a comparison of the factors—analyses of 

the water at different states of the tide and from several parts of each lagoon, estimation 

of the amount of water entering or leaving each lagoon, areas of coral growth, etc.—would 

be useful, and could not fiiil to throw much desirable light on this most complicated question^ 

Section III. The Bathymetrical Limits of Coral-Reef Builders. 

While the dredgings in the Maldive Archipelago were mainly taken to ascertain the 

general characters of the bottom and its fauna and flora in diff'erent jaositions, the situations 

were— by particular requests of various authorities on the formation of coral reefs— 

largely chosen with the view of ascertaining the depth to which the reef corals extend. 

Dredges of Naples and Plymouth designs and hempen swabs, 3 to 9 feet long, were largely 

used in addition to the Otter trawl and beam trawls of various patterns. The eff'ectiveness 

of all these in procuring corals from shallow water, where the bottom could be seen, was 

carefully ascertained, and the trawls were additionally weighted with 2 or 4 old fire-bars for 

deeper work. During the time I had the steamer for dredging I chose some of the roughest, 

and hence most likely ground, between 30 and 50 fathoms, ultimately breaking or leaving 

most of my a^jjiaratus on the bottom. Much dead coral rock was brought up, some of it 

also for giving me the assistance of trained attendants. water and dried, and the organic matter burnt off. The 

Three to ten grams were taken of each sample after it had amount of silica (SiO.,) was then estimated. The only metals 

been well mixed, the whole carefully washed with distilled found were Calcium, Magnesium, Aluminium and Iron.


consisting of blocks evidently free and some of masses showing fractures, where they had been 

broken off the bottom or still larger lumps. 

The results were mainly negative, but the apparatus being thoroughly reliable and the 

dredgings fairly numerous, they may be relied upon. Series of dredgings in the same locality 

and habitat are repeatedly counted as single dredgings. 

On the opposite page is a table showing the number of times living specimens of each of 

the different genera were obtained at various depths beyond 15 fathoms down to which the reef 

genera extend in great luxuriance. 

— 

The forms of growth are as follows : B. branching : C.B. coarsely branching : F.B. finely 

branching : S.B. spreading branches : F. foliate : /. incrusting : M. massive : S.M. spreading 

massive : S. spreading. 

A plain cross after the name, thus f , indicates that more than one species was represented. 

The genera marked with a star * are to some extent doubtful, but serve sufficiently to 

show the facies and alliances of the species. Domoseris is almost certainly a synonym of 

some other genus, but I have been unable to examine any specimens of the allied genera. 

The following genera of reef-building corals, characteristic of the Maldives, are not found 

in the collection : 

— 

Coeloria, Leptoria, Prionastraea, Mussa and Symphyllia. Goniastraea was 

only once obtained, and the Orbicella belong to species with small calicles, not found on reefs. 

The species of Montrpora and Hydnophora and to some extent of Astraea and Galaxea belong 

to forms of growth widely differing from the large, characteristic, massive colonies, more generally 

found on reefs. Madrepora with increase of depth breaks up into thinner and finer branches 

and twigs ; its stems ramify almost horizontally, and its calicles are widely separated from 

one another. Pocilloporu alone varies but little, its colonies presenting the same two common, 

finely and coarsely branching, facies of growth, usually seen on reefs. 

A few genera, not found at the sui-face, are evidently of great importance as builders 

between 20 and 40 fathoms. Of these Dendrophyllia, of which there is only one species, 

D. ramea, where found,, appears generally to form gi-eat groves, immense quantities being 

obtained ; some of its main branches were of large size, even 2 yards in length by 3 to 

5 inches in diameter. An allied genus or a sub-genus, Goenopsammia, grows commonly on 

the under, shaded sides of stones on the reef, but was not dredged. Gonipora was found 

either as fixed, large masses, of which chijjs only were usually broken ofJ", or free in mud 

or sand in a form allied to G. stokesi. Alveopora grew in large masses, usually much crushed 

when brought up, or in branches, the tips of which alone were alive. Seriatopora gave 

colonies either of extremely fine branches, or of finger-like stems. Stylophora was only secured 

on two occasions, both outside atolls, but the quantity of massive branches then brought up 

points to its being of no inconsiderable importance in this position. That the same genus 

should not be found on the reefs is peculiar, as it was one of the most numerous on Funafuti 

and other Pacific reefs. The specimens, placed under the genus Trachypora, represent modified 

incrusting Pavonia, which have taken to a deeper habitat. 

The false corals, Millepora and Heliopora, have already been to some degree considered 

(pp. 314—317). In the accompanying table they supply 7 out of the 14 times surface-reef 

genera were dredged between 36 and 40 fathoms, and 3 out of 4—the genus of the fourth 

being doubtful—between 41 and 50 fathoms. I have never observed either of these genera on a

Depth in Fathoms 

Total Dredgings 

Dredgings having Corals... 

1. Stylophorai 

2. Seriatopora + 

3. Pocillopora t 

4. Madracis 

5. Eupkyllia 

6. *TridacophyUm ... 

7. *Trachyphyllia ... 

8. *Echmophyllia ... 

9. Echinoporai 

10. ilendina 

11. Oalaxeai 

12. Goiiiastraea 

13. Cyphasiraea 

14. Hydnophnra\ ... 

15. Orbicella 

16. Astraeai 

1 7. Siderastrea 

18. Paoo7iia 

19. Sandalolitha 

20. * Trachypora t 

2 1 

. 

Packyseris 

22. *Domoserisi 

23. Psammocora 

24. Dendrophyllia ... 

25. Astraeopora 

26. Tiirhinaria 

27. Madrepora\ 

28. Montipwa t 

29. Alveopora\ 

30. Porites\ 

31. Goniopora\ 

32. Millepora 

33. Heliopora 

^ fTotal 

% 

a 

J. Reef Genera only 

P 

^ "-Genera not reef... 

Forms of 

Growth. 

1st 

C.B. 

F.B. 

C.B. 

F.B. 

B. 

S. 

F. 

F. 

F. 

F. 

M. 

M. 

M. 

M. 

M. 

M. 

M. 

M. 

I. 

S. 

F. 

M. 

B. 

M. 

F. 

C.B. 

I. 

M. 

I. 

M. 

B. 

B. 

2nd 

F.B. 

S. 

S.M. 

S.M. 

B. 

F. 

F. 

I. 

F.B. 

B. 

C.B. 

M. 

16—20 21—25 20—30 31-35 36—40 41—50 

29 

11 

45 

26 

19 

65 

34 

2 

1 

4 

5 

2 

17 

11 

2 

4 

2 

5 

3 

3 

94 

44 

50 

55 

17 

41 

16 

26 

33 

11 

20 

13 

31 

9 

30 

14 

16 

23 

5 

1(?) 

(1?) 

4(1?) 

Found ou 

Surface Reefs 

E = Rare 

G = General 

C = Common 

C. 

G. 

R. 

325


true reef flat or in the fissure zone of any Maldivan reef, freely exposed to the sea. They 

are not important— if at all—builders on the outer slope down to 15 fathoms either against 

the open ocean or the Great Maldive Sea. On the other hand they are found in great 

clumps, up to 2 or 3 yards across, in boat channels and on sand flats as at Rotunia, usually 

the colonies having more or less lamellate facies. The recorded dredgings, where the two 

genera were obtained, were all in passages or outside atolls, and both were generally found 

living together. Heliopora had previously been obtained by Basset-Smith off the Macclesfield 

bank between 25 and 35 fathoms' and by the writer off Funafuti between 35 and 45 fathoms^ 

and Millepora at about 25 fathoms, likewise off Funafuti-. Otherwise the genera were formerly 

regarded as essentially reef or surface forms. It is interesting to observe that absolutely no 

specimens of either were procured in the Maldives from between the surface and 20 ftithoms, 

although Millepora at any rate was very abundant in all the passages into Funafuti lagoon, 

to 10 fathoms in depth. The specimens of both forms were mostly in the form of wide plate-like 

branches, although one incrusting specimen of Millepora was also secured. The quantity usually 

obtained, when either of these forms was dredged, shows that they are not improbably the most 

or among the most important of the reef-builders below a depth of 25 fathoms. 

Among the other builders requiring consideration the most important is Polytrema, the 

significance of which lies in its power of binding together sand and rock. In the Maldives 

growths were obtained in practically every dredging, in which corals or fragments of rock 

were secured. In the passages Polytrema forms concentric incrustations round small pieces 

of coral or rock. Outside the atolls in soundings and dredgings it was obtained down to 

125 fathoms, and its importance is probably very great. Lithothamiiion was constantly j^resent 

in dredgings outside reefs or in passages down to 45 fathoms, protecting dead coral or rock 

below 25 fathoms. Indeed the dredgings show that it is chiefly in this last quality that 

both this form and Polytrema are important, neither below 25 fathoms providing any con- 

siderable bulk of the material of which the reefs are built. Halimeda leaves, serving to fill 

in the hollows and the interstices of the other organisms, were constantly procured living 

down to 35 fathoms, beyond which its growth appeared to gradually die out. In Mahlos 

great beds of 3'oung oysters (apparently Meleagrina margetifera) were found at 25 fathoms, 

the shells of %vhich would be of assistance. 

Solitary corals have in the list been completely neglected, most genera having only 

a minute value in the formation of reefs. Fungia is sometimes found in great abundance 

on surface reefs, but was only once dredged, i.e. between 16 and 20 fathoms. An allied 

genus, Diaseris (probably synonymous with Gycloseris), was obtained living on nine occasions 

between 25 and 40 fathoms. In five of these dredgings the quantity of coralla— principally 

dead but also living—was very large, and in a tenth haul only dead specimens were secured. 

In the north passage into Suvadiva lagoon, 36 to 40 fathoms, in one haul of a 4^ feet 

beam trawl about 2 cwt. of dead masses of rock were brought up, mainly composed of the 

dead coralla of this genus, cemented together by sand and deposited carbonate of lime. 

A second dredging of the same passage, where it opens into the lagoon, gave great quantities 

of dead Heteropsammia in addition to a number of live specimens. In the same position 

the Snapper lead three times in succession brought up specimens of the dead coralla of 

this genus, the whole bottom appearing to be almost coated by them. 

' Ann. Mag. Nat. Hist., Nov. 1890, p. 353 et seq. - Loc. cit. pp. 478—9.

RATE OF GROWTH OF REEFS. 327 

In conclusion, I may at once remark that the above table absolutely negatives my 

previously-expressed view' that the reef corals probably live down to 40—50 fethoms in 

great luxuriance. Darwin in placing the extreme depth of flourishing banks of surface-reef 

corals at 25 fathoms was entirely correct. The specimens of these corals procured from beyond 

this depth show clearly in their growth that the increased depth is deleterious to them. At 

the same time the presence of a series of other genera of corals, which evidently flourish 

iust beyond where the surface forms cease to exist, although with a considerable range in 

depth, is for the fii'st time clearly demonstrated. 

Section IV. The Rate of Growth of Corals and Reefs. 

The formation of a reef is an exceedingly complex problem, in which a large variety 

of organisms all play their parts. The rate of growth of many reefs is doubtless infinitesimal. 

Our scientific interest lies mainly in considering the probable rate of growth on open banks 

freely exposed to the great ocean currents, while the practical interests of navigation require 

as well that the rate of growth within the lagoons of atolls should be accurately ascertained. 

Our practical interests demand the consideration of the possible, maximum rate of growth, 

while for the theory we require rather the knowledge of the probable, average rates of growth. 

Freely exposed ocean banks and lagoons differ so profoundly in the structure of those 

reefs that have grown up actually on or in them, that any comparison is at first sight 

impossible. The lagoon reefs are more or less spongy structures, formed mainly of corals 

filled in with sand, while to build up formations outside an atoll requires a far greater 

complexity of organisms. The possible maximum rate of growth of a lagoon shoal is obviously 

the greatest rate of growth of corals in heiglit in that position, the sand, etc., by which 

the corals are consolidated, not being necessarily formed by the decay of its organisms. 

These same shoals consist in the first place, until they reach the low tide limit, of mere 

coral heads, and their probable rate of growth up to this stage is not unlikely to be nearly 

equal to their possible rate. In addition the possible rate of lateral growth of such shoals 

is required for practical purposes. The tendency to and possibility of such kind of growth 

has already been sufficiently discussed in previous chapters, and need not detain us here. 

It is, peradventure, sufficient to point out that for navigation the accurate fixation of the 

central point of an ordinary shoal is all that is usually required with a rough contour and, 

of course, the soundings. 

The rate of growth outside atolls is another matter. The general contour of the bottom 

is smooth, though hollows and pits occur. All its corals grow at about the same rate and 

so preserve its general contour. This doubtless is due to the strong outward cuiTcnt from 

the reef above, and is absolutely comparable to the level top of a plantation of firs, on 

a smooth, exposed hill-side. Rarely does any coral succeed in raising its head above the 

general level, and, when one does so, it is improbable that it is able to remain as a permanent 

structure. The loose material, that serves to fill in the interspace between the coral masses, 

consists mostly of coral fragments—derived principally fi-om the reef flat above—and of free- 

living Foraminifera. Lithothamnion and Polytrema turn the whole into rock, loss being 

almost an unknown factor here. The rate of growth of the whole reef is, hence, not probably 

widely different from that of the individual corals that mainly serve to build it up. Once 

1 Loc. cit. p. 478, etc. 

G. 42


more it is to the rate of growth of the corals that we must look to get an idea of the 

possible and probable rates of the reef itself 

An almost insuperable difficulty for the consideration of our problem lies in the necessity 

of determining the rate of growth of the corals at different depths. There are no fixed 

laws for different species or even genera, but the rate is mainly affected in every case by 

the environment. When reef corals have once fairly fixed themselves on a shoal, the task 

of determining when that shoal will reach the surface, is as nothing compared to the difficulty 

of ascertaining the time that has been taken by the coral larvae to so secure themselves. 

The larvae must have a firm support, must in fact build up their houses on rocks, and it 

is owing to this that the growth of new shoals in lagoons is so rare. Above I only deal 

with reef corals; the task is many times magnified when we come to consider other forms. 

The problem, in truth, is one beset with innumerable difficulties, but one of such importance 

that any results, however small, are of great interest and value. 

The facts relating to the growth of corals and reefs up to the year 1890 were ably 

summarised by Dana^ whose conclusions are best expressed in his own words :— " Whatever 

the uncertainties it is evident that a reef increases in height or extent vpith extreme slo^vness. 

If the rate of upward progress is one-sixteenth of an inch a year, it would take for the 

addition of a single foot to its height, one hundred and ninety years, and for jive feet 

a thousand years." (The italics are Dana's, not mine.) This was published antecedent to the 

appearance of Murray's full work on the influence of pelagic oi-ganisms on the formation of 

rock -, and it is evident that the possibilities of the enormous rate of increase of these and 

other organisms were not understood by Dana. Unfortunately I am unable to admit much 

of Dana's premiss, as I differ profoundly from him in regard to the structure of coral reefs 

and the mode of growth they exhibit at the present day. 

Little work has been published on the subject since Dana's resume. Agassiz gave a few 

photographs of the natural sizes of certain corals from a telegraph cable at a depth of 

6—7 fathomsl Taking the measurements from the figures of the specimens, these show 

a maximum upward rate of growth of respectively 3^, 2 and 3 inches, and lateral extensions 

of 3^, If and 2\ inches, taking the halves of the total breadth of each, in seven years. 

More recently I discussed the rate of growth of certain specimens from Fiji^, but with no 

attempt to deduce general conclusions as to the rate of reefs. Calculated out on Dana's 

method and remembering that practically the whole surface of a reef is covered with growing 

corals, the Fijian specimens would give an average rate of upward progress of 5'19 mm. in 

one year or a thickness of about 17 feet in 1000 years. 

Many of the inhabited islands of the Maldives have definite channels for theii- small 

fishing and trading boats, excavated through their encircling reefs, even the shallowest usually 

with at least 4 feet of water at low tide. The boat channels between the land and reef 

accordingly make safe harbours for small vessels, and slips on the shores serve for repairing 

the latter. These canals, or magu—a naturally formed ship's passage, such as those into any 

of the lagoons, is termed in Maldivian kandu—by the laws and customs of the country are 

cleared out according to the needs of the different districts once every 2 to 5 years. In 

Mahlos, Male and atolls more particularly under the sway of the Sultan, the law is that this 

1 Coral and Coral Island.^, 1890, pp. 123— 127, 253—2.58, ' Bull. Mas. Comp. Zonl. vol. xx. p. 61 (IS'.IO). 

and 396-397. * Proc. Camb. Phil. Soc. vol. xi. pt. iii. pp. 214—219 

2 "Deep-Sea Deposits," Challenger Reports, 1891. (1901).


shall be performed once in every 3 years. It is the duty of the atoluveri, or provincial 

governors, to see that this is carried out, and, as the duty fits in with the private interests of 

their officers, it may safely be assumed that it is properly performed. In Mahlos and Miladumadulu 

I saw—not at the time appreciating the stringency of this law—eveiy range of living 

coral growth in these canals from 1 to 3 years of age. The bottoms of some were literally 

covered with corals, and, it was quite evident, would, if left alone, in the course of a very few 

years become completely blocked uji. At Limbo-Kandu in N. Mahlos and Hurubudu in 

S. Mahlos, both of which were inhabited less than 20 and 30 years ago, the former canals could 

only be distinguished by the less consolidated nature and the narrowing of the reef, a growth 

of at least 4 feet in 20 and 30 years. At Fainu also in N. Mahlos what was originally 

the main passage, 5 feet deep, was abandoned in 1885, or 14 years before my visit. It was 

situated opposite the middle of a passage into the lagoon of the atoll, and must have been 

swept by strong currents, so that it decidedly could not have been in a position at all 

favourable for coral gi'owth. Yet the whole bottom was so studded with branching and massive 

corals that the canal was not negotiable at low tide. 

Innumerable other instances might be given, but they lack sufficient precision, whereas 

from the canal at Hulule I brought a number of corals, the maximum possible age of which fi'om 

the ova is accurately known. Hulule is the most south-easterly island of North Male atoll, and 

is situated to the south of a large faro. There is a velu of moderate size, about 6 fathoms deep, 

to the north of the island but no other land, except a single island at the north end and a 

mere rock to the south. In its west reef, a little north of Hulule, are two small passages, kept 

open by the scour of the water across the faro and round the north end of this island. Opposite 

the middle of the land on the west side lies a small pool, where the Sultan moors his private 

yacht, 4 fathoms deep by about 40 yards across. Leading to this a canal had been cut through 

the reefs to a mean depth of 4 feet at low springs. This is regularly cleaned out once in 

every three years' under the inspection of officers from Male. The island belongs to the Sultan, 

and is regularly visited by him for religious purposes, the canal being at the same time examined 

to see that the work is properly performed. My collection was obtained in February, 1900, of 

the third year, and I visited the channel a second time at the beginning of the following 

April to secure additional specimens. However, in the mean time it had been cleaned out so 

thoroughly that not a single piece of living coral could be found ; the whole bottom had been 

levelled, and the coral all removed. Any living fragments of coral, that possibly were left, could 

not in any case have continued to exist on account of the mud, with which the bottom was 

coated. The Sultan's annual visit was to take place in 1900 in the middle of May, so that it 

is safe to assume that it could not have taken place in 1897 until a month later. The 

work would in 1897 have been done before May, since later, the channel not being protected 

from the south-west monsoon, the job would have been attended with considerable difficulty. 

April would accordingly have been the last suitable month, and it is probable that its low 

spring tides were utilised for the work. The corals brought home would hence have taken 

' It was very difficult in the Maldives to accurately aseer- I have throughout generally used the Maldivan (Mahom- 

tain measurements, either of time, length, or weight on medan) year as equivalent to the European, so as to avoid 

account of Arab, or peculiar, in fact indigenous, standards possible exaggeration. One of the few exceptions is that 

being used. The numeration is in twelves, not tens, and which immediately follows, where I have allowed for the 

Hindustani, Arab and Maldivan terminologies are all mixed. difference in number of days in calculating the times of the 

An isolated, tropical race of low culture is, in addition, not Sultan's visit to Hulule. 

accustomed to think precisely. 

42—2


some period certainly less than 3 years, and probably not moi-e than 2 years and 10 months, to 

have grown up from ova to their present size. 

The physical conditions in the Hulule canal cannot be said to be especially inimical or 

favourable to coral growth. Strong currents pass in and out of the atoll between Hulule 

and Male, so that there is ample change in the neighbouring waters. The coral growth is 

luxuriant on the reefs to the west of Hulule, and the different corals grow fairly evenly in 

height, no genera being particularly vigorous. During the north-east monsoon there is a 

considerable sweeping out of mud, weed and sand from the shores of the island, which must 

be injurious to coral life. One may deduce from the appearance of the western passages 

into Minikoi atoll in the south-west monsoon, and fi-om that of many of the artificial canals 

in the Maldives opening to the east in the north-east monsoon, that in the south-west 

monsoon the bottom of our canal would be swept bare of all sediment, absolutely down to 

the rock. The same canal, too, feeds no wide stretch of water so that the currents in it would 

not be of any gi'eat force. The canal, accordingly, in the south-west monsoon should be especially 

favourably situated for the gi'owth of corals. Coral larvae could scarcely succeed in establishing 

themselves in the north-east monsoon on account of the mud, whereas the opposite monsoon 

should be most auspicious for their fixation. Indeed, it is probable that all the specimens 

would have commenced to grow in the latter monsoon, and that they would hence represent 

three growth periods of less than 3, 2 and 1 years. 

The accompanying Table of the specimens serves to explain itself (p. 331). I have not yet 

worked out my coral collections, so that the naming of the species must be taken as only ajjproxi- 

mately correct. The important point is to know the form of growth in the genus—it is very 

unlikely that the rate of growth in a genus differs materially in closely-related species—and the 

specific name, or some other indication, is given in each case to show the facies. I have added 

to the form of my table, as originally published, the approximate horizontal area each coral 

covers in its position of growth, as far as the latter can be perceived, and also the height of 

each above its true horizontal base. As the colonies had been drying for two years, I have 

only given one weighing in this state. They were then soaked in water and weighed in the 

same until the resulting weight became constant; the volume alone, however, of the broken 

fi-agments was measured. 

It is important to observe a second time that the above specimens must all have grown up 

to their present size witltin a period of 3 years ab ovo. Further, they were all obtained out of an 

area of 4 square yards, or 33416 sq. cms. Their position in the canal, some distance from its 

outer end but more or less in the centre, would certainly not theoretically have been the most 

luxuriant for coral growth, and indeed was selected rather as representative of the whole channel. 

Most of the corals were attached, and must have grown in the position in which they were 

obtained. The Fungia and two other free forms, Orbicella (No. 8) and Monttpora saxea (No. 20), 

if they did not actually gi-ow within the area, can only have originated in its immediate vicinity; 

in no case is it possible to suppose that they can have come fi-om the reefs at the sides of 

the canal. 

The rate of growth of the reef as 

methods:— (1) The specific gravity of 

a whole can be calculated 

fine sand-rock being 2-48 

for say 1000 years by several 

(average of 10 samples), the 

corals may be estimated in this condition, and will give a deposit over the area of 85 cms. 

(2) With the specific gravity 178 (see Table), the deposit would be 123 cms. (3) Taking merely 

the area 3986 sq. cms., known to be actually covered by the corals themselves, the growth.

G 

m 

a 

I 0) 

§3 

bn 

I 

9. 

10. 

11. 

12. 

13. 

14. 

15. 

16. 

17. 

18. 

19. 

20. 

21. 

22. 

23. 

24. 

25. 

26. 

27. 

28. 

29. 

30. 

31. 

32. 

33. 

34. 

35. 

36. 

37. 

38. 

39. 

40. 

41. 

42. 

43. 

44. 

45. 

Name of Coral 

Goniastraea emmia , 


„ [Astraea]) ... 

Prionastraea abdita 

„ tenella (sp. ?) 

A canthastraea grandis 

Cyphastraea savignyi 

Orbicella (sp. ?) 

Coeloria daedalea 

Hf/dnophora microcoiia 

Symphyllia sinxiosa ^ . 

Pavon ia repens 

Psa77imocora (sp. !) 

Montipora foveolata 

Montipora saxea 

.... 

. . 

Astraeopora inyriophthalma. 

Fu7igia (yonng) 

deniigera. 

Pocillopora coespitosa 

„ plicata ... 

Madrepora (stunted) 

(semi-massive) 

(clump) 

(spreading) 

Porites (dense clump) ., 

„ 

(open branches) 

Psammocora contigua ... 

Merulina (genus ?) 

Euphyllia glabrescens . . 

. 

Weight 

in grams 

' A small colony of Madrepora of a much stunted growth 

was attached to the main mass of this coral. The Specific 

81 

509 

318 

12 

218 

1094 

230 

147 

571 

325 

245 

321 

309 

967 

303 

769 

453 

1485 

28 

590 

214 

47 

25 

151 

357 

379 

452 

154 

228 

442 

531 

478 

693 

68 

83 

343 

911 

239 

463 

739 

473 

346 

295 

60 

1.34 

Volume 

in cc. 

46 

380 

212 

6 

103 

660 

128 

86 

287 

156 

199 

203 

161 

693 

145 

410 

206 

671 

15 

271 

103 

19 

10 

62 

127 

142 

171 

91 

137 

218 

248 

237 

426 

32 

37 

173 

653 

93 

2372 

5442 

348 

218 

147 

37 

89 

Specific 

Gravity 

1-76 

1-34 

1-50 

2-00 

211 

1-65 

1-79 

1-71 

1-99 

2-08 

1-23 

1-58 

1-92 

(1-39) 

2-09 

1-81 

2-19 

2-21 

1-86 

2-17 

2-08 

2-47 

2-5 

2-44 

2-81 

2-67 

2-64 

1-69 

1-66 

2-03 

2-14 

2-02 

1-62 

2-13 

2-24 

1-98 

1-39 

2-57 

1-95 

1-36 

1-.36 

1-58 

2-01 

1-62 

1-51 

Area 

covered 

in 

sq. cms. 

25 

84 

71 

7 

34 

221 

55 

22 

81 

48 

68 

72 

74 

170 

61 

113 

100 

287 

17 

84 

42 

27 

18 

47 

72 

97 

103 

57 

80 

118 

126 

123 

139 

18 

25 

33 

126 

62 

336 

216 

147 

1.55 

54 

38 

33 

Height 

iu cms. 

4-2 

7-3 

6-8 

2-1 

7-9 

5-8 

6-1 

4-8 

8-2 

6-2 

7-8 

7-3 

7-1 

10-2 

7-4 

10-1 

5-4 

11-8 

2-8 

9-6 

6-0 

2-2 

1-7 

3-7 

4-0 

3-9 

4-3 

5-4 

8-3 

8-5 

12-7 

10-7 

15-0 

5-2 

5-5 

15-6 

22-0 

130 

10-2 

9'2 

8-7 

91 

8-6 

2-3 

141 

Gravity for the genus is hence quite erroneous. 

Thickness 

as 

a sheet 

in cms. 

1-84 

4-52 

3-00 

86 

303 

2-98 

2-33 

3-91 

3-54 

3-25 

2-92 

2-82 

2-17 

4-07 

2-37 

3-63 

2-06 

2-68 

•88 

3-23 

2-45 

•7 

•55 

r32 

1-76 

V46 

r66 

1-60 

1^71 

1^84 

1-97 

1-93 

3^06 

r77 

1-48 

5-24 

5-34 

1-50 

•70 

2-52 

2^37 

1-42 

2^72 

•97 

2^70 

- Calculated from Specific Gravity of fragments. 

g


1. Massive Astraeidae 

Summary of Table.

BORING AND SAND-FEEDING ORGANISMS. 333 

outside atolls is certainly many times greater than within atolls, and in my opinion does not 

materially decrease until a depth of over 20 fathoms is attained. Until a surface reef be 

formed, or until the reef nearly reaches the surface, there is probably no outward sweeping 

of talus to spread the foundations of the whole. Interstices are filled in largely by nullipores 

and Foraminifera, or else bridged over. All the corals keep pace in their growth, and the 

rate of the whole reef would be the average rate of its corals. 

Considering all the various factors, and particularly remembering the necessarily slower 

growth at the initiation of a reef and as it approaches close to the surface, it yet seems 

to me to be probable that an oceanic shoal at a depth of 25 fathoms might well in 1000 

years, or even less, be covered with a perfect surface reef, built up by nullipores and reef 

corals. In effect, if Falcon Island, erupted to a height of about 250 feet in 1885 and now 

a mere shoal, be cut down to 25 fathoms by the end of this century—a by no means unlikely 

proposition—its place might well be marked by surface reefs, perhaps even by a perfect atoll 

considerably before the year 3000 A.D. Should these deductions be, as I believe, fairly accurate, 

a natural explanation is at once afforded of the rarity of submerged banks of all sorts in 

coral-reef areas as compared with surface atolls and reefs. 

Section V. The Action of Boring and Sand-Feeding Organisms. 

1. General. 

The skeletons of the corals and other organisms of a reef are either built up into 

a coral limestone by the animals themselves, or are worn down into mud and sand. A third 

fate may, however, at any time befall them in being dissolved by the sea-water. It is obvious 

that as a rule the smaller the skeleton the greater must be the amount of surfixce that 

will be exposed to solution. Hence sand should be more acted upon, and should suffer more 

loss in weight, than corals, shells or nullipores. Now the ground-down skeletons of these 

organisms form the greater part of the sand, and it is most necessary to examine the 

means by which their massive skeletons are broken up. 

The main destructive agents of reefs are, undoubtedly, marine animals and to a lesser 

degree plants, aided to some extent by the solvent action of the water and erosion by the 

currents. The destructive organisms have two modes of procedure. First they bore into corals 

and other skeletons, and so weaken them that they break either by their own weight or 

the motion of the sea. Indirectly they probably by their organic matter attract other animals 

to ingest the fragments and further break them down. The latter or second action, that of 

sand trituration, is of no small significance. 

In actual number, the animals that depend on sand for their food in any atoll are 

probably more numerous than the boring or free-living forms, as undoubtedly they are the 

most difficult to get any adequate knowledge of. Besides breaking down the fragments of 

rock into sand, they are the main factors in the creation of mud. The deeper layers of 

the sand of a flat pass through their bodies again and again, being in all cases ejected 

in a still finer state on the surface of the bottom. With the ebb and flow of the tide, 

with storms, etc. much of the finest matter must pass into suspension in the sea-water, to 

be, perhaps, deposited outside the atoll. The influence of this outwash on the character of 

the bottom deposits outside reefs has been thoroughly established by the Challenger expedition, 

and there is no call for further comment here.


To quote Sir John MuiTay's Summary of his Report on Deep-Sea Deposits, " Coral 

Muds and Sands cover a large area in all coral-reef regions, estimated at about 2,700,000 

square miles, including those from shallow water and also the area of the islands and of 

the lagoons and lagoon-channels. The coral-reef region of the Pacific is by far the most 

extensive, and there Coral Muds and Sands attain their maximum development, being estimated 

to occupy about 1,500,000 square miles; in the Atlantic they cover about 800,000 square 

miles, and in the Indian Ocean about 400,000 square miles '." The area in the slightest 

degree covered or enclosed by actual surface reefs in the Indian Ocean is certainly less than 

25,000 square miles, so that the space actually covered by deposits, mainly formed from the 

same, is at least sixteen times as great. As to the rate of formation of the deposit Sir John 

Murray remarked :— " Around some coral reefs the accumulation must be rapid, for, although 

pelagic species with calcareous shells may be numerous in the surface waters, it is often 

impossible to detect more than an occasional pelagic shell among the other calcareous debris 

of the deposits ^" 

The main cause of the formation of lagoons is, assuredly, the solution of the calcium 

carbonate by the water, but the outwash of mud is an important and direct subsidiary cause. 

At the same time the mud has an indirect action as well, i.e. by preventing the growth 

of coral and other sedentary organisms on the floor of the atolls, and by constantly checking 

and restricting all such growth. This was an action repeatedly observed by us, but from 

its nature one almost incapable of direct estimation. I am here, however, more expressly 

concerned with the organisms which are the cause in their individual capacity, rather than 

the effect which they ultimately produce. 

Although it is scarcely necessary, one is here impelled to refer to Darwin's work on 

"Vegetable Mould and Earthworms" in which he estimates that 10 tons of earth per acre 

annually pass through the bodies of earthworms, and are brought to the surface. The action 

of the reef organisms takes in not only the deeper sand but the surface material as well. 

It is independent of summer and winter, drought and frost, and in the smallest estimate 

could not be placed at less than 50 times as much as that of earthworms, with an erosive 

action by the average marine animal on the sand many times as strong. 

The phenomena, however, are not confined to reefs, and have been demonstrated by 

Buchanan in the deposits of the ocean' :— " As the result I was led to believe that the 

principal agent in the comminution of the mineral matter found at the bottom of both 

deep and shallow seas and oceans is the ground fauiia of the sea, which depends for its 

subsistence on the organic matter which it can extract from the mud." With this conclusion 

I cordially agree, but I do not think that the sand-feeding organisms of coral reefs have 

any considerable chemical action on the sand. The latter is always free from smell, even 

on mud flats, as off Huludu, Addu atoll, and, whether dry or wet, sulphuretted hydrogen (H^S) 

is not given off, when acted upon by acid. The sand consists of almost pure carbonate of 

lime, and, although I sought carefully for any digestive action on the sand—the reaction of 

the contents of the gut was usually neutral, rarely alkaline—I failed to find any trace of 

such in the true, sand-feeding organisms'*. The action of these forms, then, is purely one 

of trituration. 

' p. 247. •• I proved experimentally that Lobophytum and massive 

- p. 411. Astraeid corals will dissolve sand grains that may be taken 

^ " On the Occurrence of Sulphur in Marine Muds and into their coelentera. I have also found Operculina in Fla- 

Nodules, and its bearing on their Mode of Formation." Proc. helium and other Foraminifera in Coenopsammia, with their 

R. S. Edin. vol. xviii. pp. 17—39 (1890). shells completely or largely dissolved.


2. Boring Organisms. 

Nearly all the skeletons of the living reef corals in the Maldives are riddled with boring 

sponges and algae. The algae all belong to one genus, probably Achyla, and seemingly to a 

single species. The sponges are of two kinds, those which form large spaces in the coral 

skeletons, which they themselves fill, and those whose presence is more or less imperceptible. 

The latter belong to the genus Cliona and probably like the algae to a single species. Achyla 

and Cliona resemble one another in their mode of growth. Their ramifications are most 

delicate, imperceptible to the unaided eye, and wander all over the coral skeleton. In Pocillopora 

their terminal filaments extend so close to the ends of the branches that only the very thinnest 

layer of corallum separates the polyp tissues from them. When a branch of this genus is 

decalcified and the pol3rp layer carefully stripped off, either of these boring organisms will be 

seen to have formed a close-meshed network, showing accurately the shape of the original branch 

with all its twigs. 

The two genera do not in the Funafuti or other Pacific Ocean corals occur together, but 

whether they do so in those from the Maldives I cannot as yet say. To separate the two 

organisms a minute microscopic examination is required, but the presence of one or other 

in most reef corals is assured. The importance of these forms lies in the fact that they riddle 

the coral skeleton as soon as ever it is laid down. In the dead or decaying portions of 

coral masses they are not found ; indeed, they seem generally themselves to die with the coral 

they inhabit. Of themselves they do not, so far as I have seen, directly cause decay, but 

presumably they show the way to other boring organisms, which certainly are not slow to follow. 

Their importance, indeed, is not improbably extremely great, but as yet little or nothing is 

known of their life histories, or modes of growth. 

A second kind of sponge—apparently a Myxospongid—is of some importance for its action 

on corals, particularly within the lagoons of atolls. It apparently enters such coral colonies 

as are more or less dead at their attached ends—thus presenting bare surfaces not covered 

with polyjDS or epitheca—and hollows out cavities up to a square cm. in size or even larger, 

which it at once fills up with a mass of yellow or grey sponge. From one space it sends on 

its growths and excavates other cavities, thus perhaps completely riddling the base of the 

mass and causing it to fall. No connection with other boring animals was in any case observed 

or indicated, and the presumption necessarily is that it forms its cavities by the action of some 

acid secretion. The corals most affected by its growth were perforate forms, particularly 

Madrepora, but I also found it in many Astraeidae as well. An intei'esting point lies in the 

fact that this sponge seems to become more prevalent with increase of depth down to 50 

fathoms, beyond which I do not know of its occurrence. 

Of Mollusca Lithodomns (Mytilidae) is often very destructive, as it bores large, perfectly 

rounded holes up to 12 or 13 mm. in diameter through the coral masses. These often extend 

for several inches or even a foot or more straight through a colony, and, where one is found, 

there are usually a great number. The various holes seldom or never communicate with one 

another, and seem for the most part to run almost parallel. There is always a communication 

with the exterior through some dead part of the corallum, by which the animal entered in 

the first place, and the polyp tissues are sometimes broken through as well, the original hole 

then perhaps being plugged up by sponge or other growth. The animal has no preference for 

one kind of coral, but all are equally affected, the base of a Madrepore colony, the skeletons of 

massive Porites or Astraeidae, or even a thick branch of Pocillopora. Lithodomus was extremely 

G. 43


abundant in the velu of Hulule, while in Minikoi it was only once secured. Generally it was 

local in the Maldives, but, where present at all, it usually was found in considerable numbers. 

It never occurs in coral in an advanced state of decay nor in rock masses. 

A second Mollusc, a small sjDiral Gastropod, is also in places abundant in corals, but 

whether it makes its own holes or not is uncertain. It may be as is Vermetus enclosed by 

the growth of the coral. In any case it is only local, mainly affecting Leptoria and other reef- 

loving Astraeidae. 

Sipunculoidea are prominent forms in breaking up almost any large block of coral from 

any position on the reefs or from any depth found on them, but only the bases of branching 

colonies are affected. These borers are perhaps more numerous in lagoon masses than in blocks 

from seaward reefs. This may be due to the former generally being larger, and it may be that 

equally large colonies from say 10 fathoms outside and inside an atoll would be similarly 

affected. While not quite absent from dead coral-rock—of the reef flat or an uj^heaved pinnacle, 

etc.—the boring Sipunculids undoubtedly prefer a coral which is to some degree living. Their 

holes are perfectly round and smooth, and ramify in every direction through the coralla. In 

size they seldom exceed the half or third of the diameter the animal assumes when freed. 

How the holes are made is not in most genera quite clear. When in the living state, the 

bodies of none have any acid secretion, so that their holes are presumably made by friction. 

The body is slightly swollen out, and, the skin being rough, forms a firm support from which 

the animal can act. The genera represented were PJiyscosovia, Phascolosoma, Aspidosiphon, 

Gloeosiphon, and Lithacrosiphon, and an account of the species obtained with further notes will 

be found in Mr Shipley's Report on the Group (pp. 131—140). 

Polychaeta are perhaps really the most important boring animals in coral rock, although 

the actual forms are inconspicuous and of small diameter^ In coral reefs at least some specimens 

can be obtained from every rock below and between tide marks. All large coral masses are 

bored into and penetrated by their tubes, which bend and twist in every direction. The surface 

at the edge of the reef is made rotten for some inches by their borings, and the section of the 

broken base of a coral often appears as a regular sieve from their holes. The finer-textured 

corals are principally affected, but all corals and rocks are attacked, so long as they have a 

fixed base of support. Fomis with calcareous or other tubes that grow with the corals are also 

bad, as they make them peculiarly brittle, and their holes form a lodgment for other organisms, 

whose subsequent destructive work is greater. From their prevalence in every rock be it of 

coral, sand or nullipore, the total effect of the Polychaeta must be enormous, and they must 

certainly be regarded as the prime and most effective agents in the breaking down of coral rocks. 

Of the families of Polychaeta, found as borers in the corals and rocks of the Maldives, by 

far the most numerous and important are the Eunicidae, which in large numbers burrow 

into every rock and coral, extending in the latter up to and often penetrating the polyp tissues. 

They are the chief cause of the rotting of the rock of the reef flat, and are abundant in the 

lagoons as well, coral masses obtained from upwards of 40 fixthoms being riddled by their holes. 

The Lumbriconereidae are less numerous, principally affecting recently formed coral, especially 

of the seaward reefs and passages. The Scoleciformia may bore into any rock, but are not 

common except in such as are already in a state of decay. The same remark applies also to 

the Phyllodocidae, but this family was f;ir scarcer in the Maldives than at Funafuti. The 

Nereidae and Amphionomidae are not properly borers, but isolated forms may sometimes be 

found in tubes in the rock, which, if they have not made, they have certainly enlarged.


Their importance lies rather in the destruction of the slabs of beach-sandstone, in the soft 

sand under which they burrow causing them to split off. Of more markedly tubicolous forms 

Serpulidae and Sabellidae are conmion, but as to how far they are destructive I have no 

evidence. 

Prof. M'lntosh^ the great authority on the Polychaeta, whose opinion on this subject I 

requested, has been kind enough to give me the following note :— " I have not specially 

worked at the boring of Polychaeta in tropical waters, but from casual observations think 

that their action is not less than in European waters— probably more. 

calcareous rocks is very conspicuous even on our own shores—especially in 

Their action on 

the south. They 

form one of the most destructive agencies in wearing away those 

the case of dead shells on the bottom of the ocean— ubique." 

rocks— just as they do in 

" Corals form a very suitable material for boring animals. I have not the slightest doubt 

that in tropical waters the boring Polychaets, such as Poli/dora, Sabella, Dodecaria and others 

are important agents in leading to the disintegration of rocks (especially calcareous and 

aluminous) and of shells and of loose calcareous stones." 

Lithrotrya, a Cirripede, is a form, numerous on the seaward reefs of both Minikoi and 

Hulule. It generally inhabits holes in overhanging masses of the raised rock of the outer 

or seaward reefs. The animals attain a length of about 3 inches, and their holes extend in 

for about this distance from the under surface of the ledge. In suitable positions thousands 

may be present, riddling the whole surface of the rock. The regularity of their holes precludes 

the idea that they can have been made by any other organism. In life they hang downwards 

with their appendages just projecting out of their tubes, when their entrances are covered by 

water. No other Crustacea are true borers, but Cryptochirus and Hapalocarcinus^ are of 

' Vide "On the Boring of certain Annelids,'' Ann. Mug. 

Nat. Hist., ser. 4, 1S68, ii. p. 276 and also "Notes from the 

Gatty Marine Laboratory. 5. On the Boring of Polydora in 

Australian Oysters," Ann. Mag. Nat. Hist., ser. 7, 1902, lii. 

pp. 299—308, both by Prof. M'Intosh. 

In the latter paper the author remarks that Polijdora is a 

ubiquitous genus and well known as an active borer in shells, 

rocks and stones. He also quotes Prof. Leon Vaillant's 

estimate that there would be 250,000—300,000 Polydora 

ciliata in one superficial metre of the calcareous rocks at the 

mouth of the Somme. 

Mr Cyril Crossland, who has recently returned from 

Zanzibar and Pemba, has favoured me with a note on the 

Polychaeta, the group on which he has been more particularly 

working. I do not, however, agree with some of his conclu- 

sions, and accordingly quote him at length : 

" The inner part and main mass of the reefs, which are 

formed of crystallised limestone, are too hard for any boring 

organism to touch, the only effecf I have seen produced on 

this rock by any organism being the impression of the foot 

and shell of a Patella. The surface of the reef-edge to the 

depth of a few inches is soft, and this is much bored into by 

Eunicidae, the mud and sand they produce being matted 

together in this same position by filamentous algae. This in 

spite of its softness forms to some extent a protection to the 

reef edge, so that it effectively resists the action of the sea. 

The recently formed rock of the boat channel is also much 

bored, but not sufficiently to make any great diilereuce to 

its cohesion. 

— 

" Polychaeta bore more especially in living coral, one or 

two specimens being found in most coral blocks when broken 

open. I do not think their effects are of much importance 

in Zanzibar in comparison to those of parasitic and aulophytic 

sponges. However weakened the coral may be at its base, it 

will iu general remain in its position of growth. 

" The bulk of my collection of Polychaeta was found iu 

sand, or among weed and sponge. Their most important 

effects lie in the transformation of moderately coarse sand 

into fine mud. They are rare in very fine sand or in thin 

mud, seeming rather to require, to be present in any abund- 

ance, a fairly stifi mud or a sand coarse enough to cohere 

somewhat. In such positions their numbers are enormous 

(though their size is in general very small), and the amount 

of fine mud produced by them every year must be consider- 

able. Wherever the sand is broken by the spade one sees 

innumerable, fine, red threads stretching across the crack, 

these being the bodies of small Lumbriconereidae and Capi- 

tellidae. Small tubeless Terebellidae also occur, but larger 

forms, Eunicidae and Scoleciformia. are not so abundant. 

" The principal boring family in live coral is the Eunicidae, 

the commonest species attaining a length of about a foot and 

making an intricately twisted boring of corresponding length. 

Sabellidae make short, straight holes. Serpulidae render 

branches of Madrepores brittle by their tubes, which hollow 

them out, sometimes every branch of a clump containing a 

tube." 

2 Vide " Marine Crustaceans. III. Xanthidae and some 

other Crabs," in the same Part of this Publication. 

43—2


assistance as maintaining open holes in the living corals, which frequently become later centres 

of decay. 

Of other animals some Echinids and Patellids wear out holes in the rock, where they 

normally take up their positions in daylight. Ophiurids creep into any holes, however small, 

preventing them from being filled in with sand. BuneUia lives in cavities of the reef, often 

1 to 2 feet below the surface, but is a rare form, and many Nemertines retire during the 

day to holes. None of these animals, however, are so far as I am aware actual borers. 

3. Sand-feeding Organisms. 

There are on reefs a very large number of animals that swallow sand, living presumably 

on the extremely small percentage of organic matter that it contains. It seems quite certain 

that the majority of these forms play some considerable part in the grinding up of the sand, 

but in most cases the process, by which they do so, is not quite clear. It will be seen later 

that all such sand-consuming forms have peculiar modifications of the gut, which adapt them 

in a singularly efficient manner for the consumption of such food as the sand contains. 

It should here be pointed out that none of these sand-swallowing animals feed directly 

on living corals, breaking off branches, etc. The polyps are thoroughly well able to protect 

themselves against most free-living organisms. Indeed, so far as I have seen, a few Gastropods 

alone make a practice of consuming the polyj^s, leaving dead tracks over the otherwise living 

colonies. I do not know what author is responsible for the now common text-book statement 

that Holothurians browse on corals'. Even considering the anatomy of these animals, it is 

obvious that the statement cannot be accepted. Holothurians might, possibly, be able to 

suck off parts of the pol}"]) layer, but that they could regularly break off coral branches, etc., 

is clearly impossible. Bits of recently dead corals may occasionally be found in their intestines, 

but I found by experiment that small living solitary corals and fragments of living coral were 

always rejected by the ordinary Holothurians of the reef at Minikoi. The actual animals that 

conceivably could feed on the reef corals of the Indian and Pacific oceans are extremely few, 

and certainly Holothurians are not among their nvimber. 

Holothurians are, however, from their great abundance on reefs the most important animals 

engaged in .sand-consumption. The sand, wherever it is present under the stones of the boulder 

zone at Minikoi, commonly has living on its surface two or three species of brown and white 

forms, while in the sand itself a few small, transparent Synaptids are sure to be caught. A form, 

resembling Synapta ooplax, is common on lagoon beaches, often in enormous numbers. Holothurids, 

related to Stichopus chloronotus and Holothuria atra, are abundant on every reef The former 

generally affects the seaward reef-flats and the encircling reef of the atoll, while the latter is 

found on all sand-flats and reefs within the lagoons. The two species, though, may sometimes 

be observed on the same area. Other forms of every conceivable colour up to 2 feet or more 

in length are also to be seen on the surface of the sand, many covered by its grains so as to 

be scarcely distinguishable. Large Synaptids, further, come out from overhanging coral masses 

every night, retiring during the heat of the day. 

Most of the above are surface animals, but in addition to these there are numbers of species 

that live in and bore into the sand. A relatively thin, white species with dark brown spots, 

' Vide "Coral Beefs," by Cbas. Darwin, 3rd ed., p. 20. The statement, surely, does not rest on this one observation.


Holothuria maculata, was most conspicuous everywhere on the sand flats, attaining a length of 

3 feet when extended. It makes burrows, up to 6 feet in depth, sometimes bent with two or 

more openings. At Minikoi, where the sand flat of the lagoon near the light-house was at low 

spring tides uncovered for some distance, the drying up appeared to stimulate these Holothurians 

to actively extrude their sand, and the whole flat every yard or so was studded with little masses 

of their pellets, which at once on the tide rising broke down into sand-heaps. 20 out of 52 or 

these castings from an especially rich area were scraped up and measured, giving an average 

of 37 c.c. for each animal. This, if spread out evenly, would cover the whole area to a depth of 

•11 mm., or a layer of sand of over 40 mm. in thickness might be supposed in this area 

annually to pass through the bodies of this one species. In addition in every sieve full of 

sand from this same area large numbers of pink Synaptids, about 2 inches long, were obtained, 

which, if less conspicuous, probably passed still more sand through their bodies than the larger 

form just mentioned. 

Holothurians are especially adapted to sand-feeding, in that they possess a conspicuous, 

ciliated groove to the gut. Besides extruding pellets many species also, or perhaps always, 

pass the sand through their bodies in a stream. The surface forms, mentioned above, feed 

during the night, remaining during the day more or less dormant. Of C3 specimens of 

Stichopus chloronotus, obtained at dawn between the large island at Minikoi and Wiringili, 

59 had sand in the mouth part of the gut. This was absolutely the same as that covering 

the bottom, mostly clean sand with a little fine washings. The output of these forms seemed 

almost continuous during the day, and consisted of fine sand only. Of 31 specimens obtained 

about mid-day all had the fore part of the gut free and the mid part choked with coarse 

sand. A few, kept in a barrel and not allowed to feed, extruded some of their sand in pellets, 

but most retained it for 3 or 4 days, only getting rid of the finest particles. In ten 

specimens, kept in a sunken barrel and allowed to feed on fine sifted sand only, the mid 

part of the gut was found after 5 days to be still filled with coarser particles than any, which 

the animals had been given. 

A Holothurian dredged from 43 fathoms, E.N.E. of Havaru-Tinadu, Suvadiva, was singularly 

interesting. It came fi-om an area of the finest mud, which extended for 1^ miles in all 

directions from the spot where it was dredged. The mid-gut was, nevertheless, full of relatively 

large fragments of coral, Halimeda leaves, etc., the coarseness of the contents approaching such 

sand as ordinarily covers the bottom at 20 fathoms under a relatively strong current. 

The sand of the mid-gut of all reef Holothurians, that I have examined, is always seen to 

be clean and the particles more or less rounded. In addition there is little loss on washing, 

while the sand in the first 3 inches of the gut commonly loses 2—8 per cent, of its weight in 

this process. Indeed, there is no doubt but that the coarser particles are detained in the gut 

for a considerable time—and probably worn down—while the sand and mud is by some means 

—presumably the ciliated groove— passed onwards. The extrusion of the whole gut and its 

subsequent regeneration is a process which commonly occurs in nature. It, not improbably, is 

for the jjurpose of getting rid of the very coarse sand, the exertions of the animal not being 

able to force it out in the form of pellets. 

Of course different kinds of Holothurians may behave in diverse ways, but the total effect 

even of the two surface forms mentioned above must be enormous. The weight of sand, 

when dried, from 4 average specimens of Holothuria atra, taken in the early morning, was 

297"3 grams. Of this 44"3 grams were extruded as fine particles into the bucket in 5 hours.


32-5 grams were found in the mouth or first part of the gut, there remaining for the rest of the 

intestine 220'5 grams of very coarse sand and fragments. A single, rather larger specimen, 

taken while evidently still feeding, had 190-7 grams of sand. Five other specimens, also taken 

in the early morning, extruded in the first 12 hours 47-9 gi-ams of mostly fine matter. In the 

following night the coarse sand began to be got rid of 49-4 grams being weighed making 

97'3 grams for the first day. In the second day 121-4 grams were extruded, in the third 

99-3 grams, in the fourth 67 grams and in the fifth 22-5 grams. The experiment was then 

concluded, 31-7 grams being weighed from the guts of the specimens, making a total weight of 

sand of 439-2 grams. 

The specimens, recorded above, were obtained in fine weather in August, but of 5.5 specimens 

examined on July 6, 1899, after bad weather of some days duration, 19 had no sand in the gut 

at all, and only 18 of the remainder in the anterior part, showing that they had been 

feeding. The experiments required an accurate means of dividing the sand into its differently 

sized constituents. As it is, they merely show that the coarser particles are retained in the 

gut—being necessarily to some extent reduced in size—and also that there is in certain 

species a continuous passage of fine matter down the gut, presumably along its ciliated fold or 

groove. The latter or some similar organ is characteristic of most true sand-feeding animals, 

and probably in all cases functions in the same way. 

Of other Echinoderms the Echinids' are also true sand-feeders, the gut in most forms 

being generally choked up with sand or small rock fragments. These animals, however, are 

of no gi-eat importance on coral reefs, the most numerous forms living on the reef flat, 

boulder zone or between branches of corals. Echinomus cijclostomus was found in some quantity 

in the sand of the flat at Hulule. The adaptation of the sub-order to this mode of feeding 

is seen in the animals possessing a fuiTow to the intestine or one or two siphons, which 

undoubtedly subserve the same function as the groove in Holothurians. 

Ptychodera is also of great importance as a sand-feeder, though how far it actively 

triturates the sand— considering its feeble musculature—is dubious. The presence of ciliated 

grooves in the hepatic and abdominal regions of the gut indicates that the sand may be 

for some time retained, when some breaking down would be sure to be accomplished. The 

ejection of the sand is a rapid process, only taking a few minutes—all the species live in 

the sand, some having burrows of poor construction—and occurs at the surface, the animal 

at least in P. carnosa" slightly extruding its cloaca. No autotomy—so far as I have seen 

from the examination of several hundred castings—takes place in nature. The animal after 

ejecting its sand retreats again, but in P. flava and in P. cariiosa still carries with it more 

than two-thirds of its original amount of sand. Further P. flava, if not irritated, retains 

its sand for a long time, attempts to keep the animal, until it had cleaned itself naturally, 

being quite futile for 4 days. 

The importance of Ptychodera, where found at all, lies in its great abundance. The 

surfaces of sand flats throughout the Maldives are studded with the castings of P. carnosa, 

often 100 c.c. or more of sand. As Dr Willey said of them in the S. Pacific, " they form an 

important feature of the landscape at low tide^" Even more abundant in the sand of the 

lagoon at Minikoi was P. flava, but its distribution in the Maldives was local. Where it 

occurred, however, a single handful of sand was often found to contain 4 or 5 specimens. 

' See Prof. Jeffrey Bell's Report on the Actinogonidiate the collection, for the names of these species. 

Echinoderms in the same Part of this Publication. ^ " Enteropneusta," Willey's Zoological Results, p. 256 

- I am indebted to Mr K. C. Punnett, who is working out (1899).


Apparently the same species often lives under beach sandstone masses, at Maduwari in 

S. Mahlos being present in enormous numbers in this position. Spengelia was also obtained, 

but, although a sand-feeder, was nowhere found in sufficient abundance for it to have any 

appreciable effect on the sand. 

Next in importance come the species of the genus Sipimculus, which likewise possesses 

a ciliated groove to the gut. Mr A. E. Shipley, who has had considerable experience of 

tropical forms, in considering the Gephyi-ea (Cainb. Nat. Hist., vol. ii. p. 422) remarks, " The 

food of Sipunculids seems to consist almost entirely of sand and their only nourishment must 

be such small microscopic organisms or particles of animal or vegetable dehris as are to be 

found mixed with the sand. The alimentary canal is as a rule quite full of sand, and yet 

in spite of the tenuity of its walls they never seem to be ruptured. If the contents of 

the digestive tube be washed out with a pipette, it will be found that it requires con- 

siderable force to dislodge many of the sand-particles lying next the wall. These are more 

or less imbedded in crypts or pockets of the wall, and, as the sand passes along the intestine, 

they probably serve as more or less fixed hard points, against which the sharp edges of 

the sand particles are worn off. Amongst the sand are usually to be found pieces of shell, 

sometimes with a diameter equal to that of the alimentary canal; these are usually rounded 

but their angles may have been removed by attrition before they entered the mouth of the 

Sipunculid." 

The animals of the genus (Sipimculus) are extraordinarily abundant on all coral reefs 

in certain positions, such as under dead corals or masses of rock. The quantity of sand 

that passes through theii- guts must be considerable, but much of it seems to be retained 

for a long period. It is too almost impossible by anaesthetisation to get the gut free from 

sand. The castings are relatively both small and fine in texture. The quantity of sand 

passing through the gut does not appear to be great, but what passes is much triturated. 

Perhaps therefore the total action of these animals may be of more importance than that 

of any other group. The species of our collection have already been reported on by 

Mr Shipley, under each its distribution being noted. I may, however, remark that S. indicus 

is found in large numbers on practically every sand flat in the Maldives. 

Of other sand-feeders Thalassema may be mentioned, of the contents of the gut of which 

Shipley has given a list (p. 129). The genus is, however, rare on reefs. Polychaeta commonly 

swallow as they burrow in the sand, but I have no reason to suppose that the sand forms 

—although often very numerous—triturate the sand to any notable extent. This does not 

quite agree with Mr Crossland's view (p. 337), but against this may be mentioned MTntosh's 

observation that the deep-sea Challenger forms often had Foraminifera and Radiolaria in their 

guts in an almost perfect state'. Much material, especially on the more muddy flats, must 

nevertheless pass through their bodies, and cannot but be to some slight degree affected. 

Section VI. Beach Sandstone. 

Large, linear masses of a friable sandstone, extending sometimes for great distances along 

the shores of the islands, are characteristic of coral atolls in whatever part of the world 

they may be found. So far as I have seen in the Maldives and elsewhere, these masses 

only occur in their tyijical condition (1) where there is a fringing reef or a sand flat of 

greater or lesser breadth extending out from the shore, or where the beach is by other 

' "Annelida Polychaeta," Challenger Reports, p. ix. (1885).


means protected from the direct force of the waves; (2) where the beach is made up 

practically entirely of carbonate of lime formations ; (3) where the beach is formed principally 

of sand and not of masses of rock; and (4) where the beach is at rest so far as growth 

outwards is concerned or washing away. 

In respect to the first of the above conditions it is necessary that the beach for a sandstone 

formation to be found should be to a large extent protected from the heavy ocean rollers or 

the smaller but perhaps more persistent influences of the waves within large atolls. At Maduwari 

(Fig. ,30) a little sandstone is found to the north of the island at the south side of an incipient 

lagoon. The beach is, however, protected by the north-east horn of the island, and the velu is 

as yet both shallow and small. 

Each island, while forming land of a fliro or atoll, has generally its own circumscribing or 

fringing reefs. If the island be situated on a faro as Hulule, Male atoll, or most of the islands 

to the west of North Mahlos, the reefs may be on one or all sides far distant and connected 

rather with the encircling reef of the faro. In all cases such an island lies on the reef, or is 

joined to the gi-owing part of the reef on one or more sides by a .shallow flat, no velu in the 

Maldives having even a single isolated island arising within it. The island indeed may have 

beach sandstone on any of its shores, but on the side towards the velu, unless there is a 

considerable sand-flat, beach rock is absent. 

Isolated islands, which cover the greater part of their reef such as most of those in 

Miladumadulu and to the east of North Mahlos, may, where other conditions are favourable, 

have sandstone on any side. That there should be a definite protecting flat or reef of some 

sort is, nevertheless, clearly necessary. On the seaward and lagoon ends of most of the encircling 

islands of Miladumadulu and Mahlos there is generally no sandstone. Sometimes to seaward 

the shore is rocky, but very generally sand is found of not greater coarseness than that 

which forms the rock of many of the lagoon islands. A comparison shows that the explanation 

IS to be sought in the extent of the protection, i.e. in the breadth of the fringing reef 

Thus on the east or seaward side of the three neighbouring islands of Kenurus, Fainu and 

Inguradu the reef is respectively about 30, 200 and 60 yards broad, and sandstone is only 

found on the corresponding shore of the second island. 

The reason that there is no beach rock on the lagoon shores of so many of the encircling 

islands is very largely the same, particularly in the atolls mentioned above. The fringing reef 

is generally narrow or almost non-existent, and the sand washes to and fro on the beach with 

every tide. The whole beach, too, is never at rest nor in one condition for any length of time. 

The currents on each side of the island in the one monsoon form an eddy behind it, piling 

up sand, which the other monsoon, sweeping across the atoll lagoon, removes so that the beach 

IS restored almost to its former state. For the same among other reasons the corals of the 

shore, alternately nearly killed by the sand and growing vigorously, are off many islands 

unable to form a definite fringing reef The conditions are best seen on the east and west 

sides of the atolls, through the passages in which the currents attain their gi'eatest force. 

Even to the north and south in the more open atolls sandstone is rarely found on the 

beaches of the islands towards the lagoons. To the south of Mahlosmadulu, however, between 

Hitadu and Defuri the rock is found just as fi-equently on the lagoon sides of the islands as 

towards the passages between them. 

The beach in the Maldives is in most places formed almost entirely of carbonate of lime 

formations. Near villages, where much organic matter is present—from the soaking of coconut 

husks for coir on the reef-flat, etc.—and in the more enclosed parts of Addu lagoon no rock

BEACH SANDSTONE. 343 

occurs on the beaches. In Ceylon, where silica is always met with to a very considerable 

extent in some form or other in the beaches, my examination—extending round more than 

the half of the coast-line of that island— failed to find any tyjaical formation of beach sandstone 

or indeed any trace of formation at all, except where the land above was of coral origin. In 

many parts the other conditions were perhaps not favourable, but in others looked eminently 

so. In any case the presence of even 5 per cent, of silica seemed to prevent any extensive 

building up of the sand of the beach into layers and terraces, typical of the appearance of 

the beach rock on coral islands. At Rotuma off Noatau, Oinafa and Pepji', where a typical 

formation exists, the beach was built up of almost entirely the same constituents as those which 

form the shores in the Maldives, the land in Rotuma for some distance behind the beach being 

in the above positions of coral formation. 

Even the finest textured specimens of the sandstone show their constitution to the 

unaided eye. Of the very numerous pieces, which I broke off, none were in any way 

homogeneous, but all could be clearly seen to have been formed of sand grains of varying size. 

Where the sand was of extreme fineness, no rock was ever found. Minikoi has near the 

village on the lagoon side, where the conditions appear in many places exceedingly favourable 

for the formation of the rock, such a sand on its beach, but there is no trace of any 

consolidation into rock. Along the west side of Hulule, the sand is perhaps a trifle coarser 

but there is no sandstone except near the south point, round which coarser material is swept 

up on to the beach. Of coarseness there is no limit, the rock sometimes consisting of 

pebbles with the interstices filled in by sand. Indeed, it is only essential that there shall 

be such an amount of the latter that the surface of the beach is smooth, all the interspaces 

being filled in by the sand. The coarsest material on a beach is naturally found at its base, 

and in correspondence the sandstone usually increases in fineness, the higher it lies above the 

low tide level. 

The beach sandstone is everywhere in the Maldives perfectly distinct fi-om the raised 

rock of the islands, which is a submarine formation difiering radically in its constitution. 

Both rocks, if in the same position, i.e. on the beach, would be affected by the same conditions, 

and might hence in external appearance resemble one another. The structure of the raised 

rocks has already been dealt with (pp. 35, 162, etc.), but it cannot be too strongly emphasised 

that the formation of this sandstone can only take place on the beach and between tide-marks. 

Its constituents show all the characteristics of such a formation, being much broken, angles 

rounded and surfaces pitted. Among them may be recognised pieces of coral of all the kinds 

found on the reefs or in the raised rock, but branching species especially of the genus Pocillopora 

are by far the most abundant. Small Molluscan shells and fragments of shell are common. Bits 

of nullipore, leaves of Halimeda and similar algae, spines and ossifications of Echinoderms, 

Crustacean remains and shells of Foraminifera make up the residue. The only constituents, 

not of lime formation, sometimes found are more or less decomposed fragments of pumice and 

sponge spicules and remains, but all these are relatively scarce, and do not in the Maldives 

form together more than '1 per cent, of the total analysis. For the constitution of the rock, 

however, its mode of formation and its method of occurrence may best be considered. 

The sand rock presents in its typical development on any beach a series of sloping 

terraces, separated from one another by steps. These terraces slope at the angle of the dip 

of the beach or slightly less, and the step from one to the other is about 5 inches and extends 

1 Vide "The Geology of Rotuma," Q. J. Geo. Soc. vol. liv. pp. 1—11 (1898) and "The Coral Reefs of Funafuti, 

Rotuma, etc." loc. cit. pp. 438—44 (1898). 

G. 44


at right angles to the slope. The appearance would hence be that of immense stone slabs, all 

duly squared and laid on one another against a sloping bank. Sometimes there is as it were 

a single slab, sometimes 9 or 10 apparently on top of one another. Often there are two or 

more lines of such masses in a beach, each of one or more terraces, separated by hollowed 

out sandy areas, and yet perhaps more often a single line at the base of the beach from 

the half tide to the low water mark. Where the beach is steep or ends in a cliff, there 

may perchance be as at Boni-Kodi, Minikoi (p. 32) an induration of the sand of that cliff, 

but marked areas are only found on the shore, where the slope does not exceed 10°, and the 

beach consequently is of considerable breadth. 

The varying conditions can of course best be seen by definite instances in different atolls, 

which will be found in Apjjendix B. to this paper. The greater part of the evidence also 

that any beach, where such formation is going on, is being washed away rather than growing 

outwards on its reef must likewise be sought in the same place. It is, however, clear from 

the consideration of the mode of formation of the sandstone that such must really be the case. 

The first appearance of the rock on different beaches varies considerably. It commonly 

commences as a single broad line at the base of the beach, where it passes into the sand 

or reef flat. Such a layer merges into the sand of the beach above and into that of the 

flat below. Usually its rock is very soft, and can be easily dug out by a hammer or 

crowbar. It does not, however, remain long in this condition. If the beach is growing 

outwards on the reef, it becomes covered up with sand, and can only be traced as a slightly 

more consolidated layer in the sand of the island. More often the waves overtop the layer, 

and the sand above it is washed out, or the sand above may be removed by the wind. 

The layer on the face of the beach has now become a definite terrace. 

When the sand above the layer has been removed to a dejith of about 5 or 6 inches 

from the face of the beach, the first layer more or less protects the beach from further 

encroachment, and a fresh layer commences to form. By this means 3 or 4 layers may be 

found on a beach, the lowest merging gradually into the sand of the flat and the highest 

almost reaching the high water mark. The water after every wave, that runs up the shore, 

has somehow to reach the sea again. It naturally is hindered by each layer, along the top 

of which it flows to make its escape 

in wearing away— partially by friction 

at the lowest 

and partially 

point. Its action here is twofold, firstly 

by solution—the top of any layer, thus 

reducing it greatly in breadth, and secondly in undermining the layer, forming natural crevices 

by which the water joins the sea again. By this means more and more layers may be 

formed, in one place on the beach at Duravandu, South Mahlos (Fig. 75), seven having been 

thus fashioned. The water in its escape off the beach consolidates the sand under the top 

layer of stone, and the second layer accordingly may be traced under the first. In a section 

owing to this action all or most of the layers may be perceived, each layer being less 

consolidated than the one above it, until about the third or fourth merges into the sand of 

the island. 

The natives are thoroughly well aware of the second or undermining action of the sea, 

and use it largely for obtaining their building material. A firmly consolidated layer is chosen, 

and, where it immediately overlies the layer beneath, its top is hollowed out so that the 

water may find a resting-place. When in a year or two the layer has become more or less 

undermined, a series of cross-cuts is made with the result that in another year the whole 

of the top layer can be wedged off in a series of slabs. In one of the beaches of the island 

of Male this action even on coral rock was clearly seen in a square about 4i feet across, cut

Fauna and Geography, Maldives and Laccadives Plate XVI 

i-'iG. 1. Ueach Sandstone to NE. of Turadu Island, S. ilalilos Atoll. 

Fig. 2. yuaiiying coral rock at Male Island. 

To JMC ;• J44

Fauna and Geography, Maldives and Laccadives Plate XVII 

Fig. 

Fig. 1. Sandy Beach to SE. of Hulule Island, Male Atoll. 

"2. Elevated mass of coral rock on the sand flat to east of Hulule Island, JIale Atoll. 

To fac: p. 344.

J3 

J3 

BEACH SANDSTONE. 345 

in the beach, 5 to 6 inches deep, with a gutter for the water to escape (Plate XVI.). 

— 2 

1 

1 

S 5 

> ~ 

3 "5 

5 fi 

5'S 

o ^ 

346 J. Stanley gardiner. 

300 feet on to the reef, as well as the remains of two series almost parallel to the beach 

at distances of 270 and 530 feet from the same. 

The action, which forms the rock, is quite clear and requires little comment or explana- 

tion. The sea twice in the 24 hours covers and recedes from the beach. In a tropical 

region the sand may be said to be twice wetted and dried. In the latter process the salts 

in the sea-water are deposited on the sand grains. Some are at once redissolved on the 

tide again covering the beach, but the carbonates and the sulphate of calcium largely remain, 

in course of time filling up the interstices between the sand grains and binding them 

together. The sulphate of calcium later becomes largely replaced by the less soluble carbonate, 

a rock being ultimately formed of almost pure carbonate of lime. The rock is naturally 

built from the surface downwards, the drying up and fresh wetting by the sea being mainly 

superficial. The thickness of the layers, 5 or 6 inches in the Maldives, probably represents 

the mean depth to which the drying up of the surface is effective at low tide. That the 

sand must be formed necessarily in the first place of almost pure carbonate of lime remains 

is probably due to the more powerful attraction that bodies of the same or like constitution 

have on one another together with the restriction of the variety of the crystalline forms 

that would occur in the beach ^ 

From the consideration of the foregoing account of the beach sandstone it will be obvious 

that almost any conceivable complication may arise in its appearance and distribution off 

any island that may be washing away. In nearly all cases the slope of any mass is that 

of the beach, of which it originally formed a part. The masses in course of time become 

more and more indurated with carbonate of lime and of great density and hardness. Where 

the beach is washed away and they lie on the flat, the terrace arrangement may disappear, 

and they will then become separate, long, irregular blocks, more or less rounded at the top. 

In this state they resist the action of the sea even more than the coral conglomerate, and 

where all remains of the latter may be lost these masses often are left. It is obvious then 

that from the study of such masses off any island or on any reef the former extent and 

contour of the land may be deduced with considerable certainty. The erosion of land in 

the Maldives, the formation of flats at about the low tide level by the washing away of 

the land and the hollowing out of such flats to form first pools, then velu or definite lagoons, 

may absolutely be traced. The facts speak for themselves, and—if my views as to the 

formation of this rock be correct, of which I can have no doubt—I claim to give indubitable 

proof that the conceptions of Murray as to the formation of lagoons and my own opinions, 

enunciated in Chapter VII. of this j)aper, rest on a firm and correct basis. 

' The skeletons of the organisms that form the sand are in the instances mentioned above (p. 343), is not however 

generally of calcite or arragonite. Most of the deposit of quite clear. 

calcium carbonate is in the first place in the amorphous It is interesting to notice that the natives of Suvadiva 

state, subsequently metamorphosing to the crystalline form make use of this indurating action of the tidal waters to 

of the remains of the organism nearest to it. This deposition 

of amorphous material may be due to the constant presence 

harden the corals of which they make gravestones. The 

coral— generally a mass of Pori'teareHOsa—is roughly squared 

of a small trace of organic matter, hindering crystallisation. and then deposited for a year on the beach between tide 

The reason why a relatively small amount of organic marks so that the pores may be filled up, the whole then 

matter should prevent the formation of beach sandstone, as wearing much better when placed in position. 

(To he continued.)

The fauna and geography of the Maldive and Laccadive ...

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