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Show 6 8 8 SIR C. ELIOT ON NUDIBRANCHS [June 19, much paler than Alder and Hancock's, but has a faint pink tinge in places, particularly on the rhinophores. In any case, Phyllobranchus orientalis A. & H. is the type of the genus, and the points in doubt can probably be settled by an examination of specimens from Ceylon. Phyl. viridis B., from the West Indies, and Phyl. borgninii Trinchese, from Naples, seem to be distinct. E l y s i i d ^e. Though the genera Elysia and Placobranchus are clearly distinguished, it does not seem to me that the differences between the two groups called by Bergh Elysiidae and Plaeobranchidce are sufficient to constitute two families. The whole family (comprising Placobranchus, Elysia, Tridachia, Thuridilla, Elysiella, and Bosellia) is nearly related to the Limapontiidse, which differ in the reduction of the tentacles, the absence of lateral expansions of the body, and the slight ramifications of the liver. Elysiella and Bosellia seem to be connecting-links, but neither genus is well known. The genus Thuridilla is well characterised: there is a buccal crop, and the anal papilla is median and posterior as in Alderia. But the distinction between Elysia and Tridachia is less satisfactory. In the latter genus the wings are very ample with crinkled margins, and in the type species (T. crispata) united behind the head. But this connection between the two wings seems not to occur in the other species. Bergh (Journ. Mus. Godeffroy, i. 1873, pp. 79-80) gives a list of twenty species of Elysia. Of these, the Elysia sp. Schramm may be omitted. It is almost certainly identical with one of the species created by Verrill, and, as it is nameless, has no claim to be maintained. Elysia nigropunctata (Pease) 1871 appears to be the same as the earlier E. punctata Kelaart 1859. I have not been able to identify the animal cited as Elysia neapolitana d'Ch. without a reference. Since the publication of this list several species have been described, of which E. lineolata Bergh seems to be clearly a synonym of E. coerulea Kelaart. E. hendersoni Eliot is not characterised in sufficient detail. Other species are :- 19. E. dubia Eliot. East Africa. 20. E. ornata Verrill. Bermuda. (There is a Pterogastron ornatum Pease, which may be an Elysia and have priority for the specific name.) 21. E. subornata Verr. Bermuda. 22. E. flava Verr. do. 23. E.picta Verr. do. 24. E. papillosa Verr. do. 25. E. thysanopoda Bergh. Malay Archipelago. 26. E. haingsisiana Bergh. do. 27. E. crispa Verr. Bermuda. |
