Chap. HI. 



GENERA OF TRIONYCIIID^. 



401 



were fountl iii lurge ([uiiutitius in the stomach of a specimen of Trionyx ferox, the 

 type of the genus, examined shortly after it had been caught. Simihvr fragments 

 were foimd in tlie faeces of other specimens preserved ahve. 



The type of the genus Platypeltis is the Tr. ferox, Schw. It is the ohlest 

 species of this fiimily known from North America. It was first described Ijy Dr. 

 Garden of Charleston, in a paper printed in the Philosophical Transactions of 

 the Koyal Society of London, in 1771, from which all later writers have bor- 

 rowed their information, until Major LeConte, Dumeril and Bibron, and Dr. Hol- 

 brook^ gave a fuller account of this species. I have little to add to their descrip- 

 tions ; but these authors are certainly all mistaken in considering this species 

 as identical with LeSueur's Tr. spinifer. Not only are Tr. ferox, Schii'., and Tr. 

 spinifer, LcS., distinct species, but they belong unquestionably to different genera, 

 as a comparison of the skulls will show at first sight. I have compared large 

 series of specimens of both kinds, from the very young to adults, and can speak 

 with confidence upon this point. Though Fitzinger unites also Tr. spinifer and 

 ferox as synonymes, I have thought it preferable to adopt tlie name he proposes 

 for this genus, and assign to it a definite meaning, than to frame a new one, 

 which in the end would appear co-extensive with Platypeltis. 



Pl.vtypeltis feuox. Fits? This species is only found in the Southern States, 

 from Georgia to Western Louisiana. Dr. W. B. Daniel has sent me many speci- 

 mens from Savannah, its northernmost station in the Atlantic States. It abounds 

 in the St. John River of Florida (Bartram, LeConte). I am indebted for many 

 specimens from Western Georgia and Western Florida to Dr. Gessner, of Colum- 

 bus, and Mr. Eppes, of Tallahassee. Dr. Nott has sent me others from Alaljama. 

 especially a series of very young ones. To Professor Chilton, of New Orleans, 

 I am indebted for specimens from the Lower Mississippi ; and to Mr. Winthrop 

 Sargent, of Natchez, for the largest specimens I have ever seen or heard of, one 

 of which measured eighteen inches and a half from the front to the hind mar- 

 gin of the carapace, and sixteen across. 



' Compare the works ([. a., p. 30, for further ref- 

 erences, but exclude from tlieir synonymy every tiling 

 that relates to Tr. spinifer, LeS. 



- The names most frequently applied to this spe- 

 cies, by different authors, are Testudo ferox, Triony.K 

 ferox, Tr. cju'lnatus, Tr. georgicus, Tr. Bi-ongniarti, 

 Tr. Bartraini, Tr. Ilarlani, Aspidonectes ferox, Asp. 

 cai-inatus, and Gyninopus spiniferus. Tiic external re- 

 semblanee between Plalyjiellis ferox and Aspidonectes 

 spinifer and asper, is so great, tiiat I am not sur- 



51 



prised that they have been confounded, or even delib- 

 erately considered as identical. We have, in fact, a 

 case here, of which a few other examples only are thus 

 far known, in which, under the most surprising simi- 

 larity of external appearance, marked structural pecul- 

 iarities, amounting to generic differences, are hidden. 

 I have already pointed out such cases in the genera 

 Phoxinus and Chrosomus, and in tlic genera Carpi- 

 odes, Bubalichlliys, and lehtliyobus, among Cypri- 

 noids (Amer. Journ. of Sci. and Arts, 2 J Jer. vol. 19, 



