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 



