Note 150 — ORDER II.—ABDOMINALIA.

M. Milne Edwards would, perhaps, in accordance with the profound views lately propounded by him on classification, consider Cryptophialus as an extremely modified, and, to a certain extent, degraded member or satellite of the type of the Lepadidæ; but I do not myself feel able to draw a line of distinction between the being a very abnormal member of one group, and belonging to a distinct group. I may add that I have several times tried to persuade myself, with no success, into the belief that I have somehow misunderstood the homologies of the thoracic segments and cirri of Alcippe and Cryptophialus; for if this were so, the two genera could be brought into much closer relationship; but with any conceivable amount of error on my part, there remains the great difference in the metamorphosis, not to mention the palpable differences in the cirri, the parts of the mouth, and in the whole course of the alimentary canal.