Dr. J. E. Gray on the Species of Crocodiles. 265 the side of each. Anus placed in a depression at the posterior extremity of the body. Foot yellowish white, linear, and squared in front. Length upwards of a quarter of an inch. A few individuals of this species were obtained, last October, in brackish-water pools at the mouth of Hylton Dene, near Sunderland, associated with Alderia modesta, on a Conferva ( Vaucheria submarina ?) . The same auimal, apparently, was taken by Mr. Muggridge and Mr. C. Spence Bate, in Loughor Marsh, South Wales, in 1849, similarly associated, and was figured by the latter gentle-man in the Report of the Swansea Literary and Scientific Society for 1850, where it is named Limapontia nigra. It is, however, readily distinguished from that species by its greater size, more depressed form, and wider lateral expansion, by the backward position of the anus, and the more branched hepatic organ, be-sides other minor characters. Mr. Spence Bate's specimens seem to have been nearly twice the length of ours. This species comes very near to the Fasciola capitata of Muller, perhaps more so than the Limapontia nigra, which has been referred to that species by Professor Loven; but as Muller had not observed the characters by which these two species are more especially distinguished from each other (namely, the position of the anus and the branching of the liver), we think it better to consider our animal as new than to revive an old name that may prove to be erroneous. XXVI. — A Synopsis of the Species of Crocodiles. By Dr. J. E. Gkay, F.R.S. &c. The distinction of the species of Crocodiles has hitherto been one of the difficult problems in systematic zoology; and there-fore I believe that it may be of some slight use to lay before the readers of the ' Annals' the result of my examination of the very large collection of Crocodiles, of all ages and from various locali-ties, which are contained in the British Museum. Knowing the difficulty that surrounds the subject, I have made great exertions to obtain specimens from different countries ; and the examina-tion of these specimens has shown that the characters of the species, when allowance is made for the changes that take place in the growth of the animal, are quite as permanent as in any other group of Reptiles. One of the difficulties in distinguishing the species of Croco-diles arises from the changes that take place in the form of the head during growth. When the Crocodile is just hatched, the
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