This large nudibranch species is easily mistaken for a Dendrodoris carbunculosa and I must admit to doing so with particular individual.  The difference can be subtle, especially if you have no access to the underside of the animal.  The D. carbunculosa lacks markings whereas the D. turberculosa has obvious white spots, its notum is more transluscent and its tubercles more ornate.  When Cory Pittman caught my mistake in identification he noted that this animal also has diffraction lines present, tubercles that are more complex and marginal folds that extend to tje edge.  This is why I always direct people to his and Paula Fiene’s Sea Slugs of Hawaii site for further information!