After spending a little more time sorting, cleaning, magnifying, and researching, here are the final additional fossils identified from the Stone City Bluff. Some may be off a bit (the various Sinum are pretty similar, as are the variations of P. Vetusta). In addition, though, I have what appears to be an algal fruiting body, something I haven't seen in many of the guides for this site.
Bivalves: Left to right, Corbula deusseni, Diplodonta petropolitana, and likely Crassotrea frionis, or some other oyster. The first two are ratehr small (less than a centimeter each), the last is much larger, at around 8cm.
Gastropods: Row 1 - Architectonica scrobicula and Natica semilunata. Row 2 - Ficopsis texana and Turricula plenta. Row 3 - Levifusus mortoniopsis and Scalina trapaquara. Note how similar T. plenta is to P. gabbi, the easiest difference to spot being the columnella fold on T. plenta (absent on P. gabbi). In my collection, while I have plenty of smaller P. Gabbi, none of my T. plenta can match the size of the larger P. gabbi.
Pseudoliva and Sinum, variations on a theme: So there are many variations of Pseudoliva vetusta, and lots of similar Sinum sp. Here are a few attempts to sort through for more specific identification. First row - Pseudoliva vetusta linosa and Pseudolivina vetusta. Second row - Sinum inconstans and Sinum declive. Third rwo - possibly Sinum arctatum (or a heavily eroded S. declive...)
Corals and Bryozoans: Row 1 (Corals) - Balanophyllia sp. and Archohelia sp. Row 2 (Corals) - Turbinolia pharetra and an unidentified colonial coral. Row 3 (Bryozoans) - Schizorthosecos interstitia and an unidentified encrusting bryozoan.
And the rest: Row 1 - possible algal fruiting body, and a comparison of the different levels of preservation of cone shells (note the unusual complete lip on the middle shell). Second row - part of a nautiloid siphuncle, a possible fossil byssal plug on a clam, and the drill hole from a predatory snail.