Chap. I. SPECIAL CLASSIFICATION OF TESTUDINATA. 251 



one of which is the well characterized genus Cinosternum of Spix. The opportuni- 

 ties I have enjoyed for the examination of the representatives of these genera have 

 satisfied me that the sexual differences among them are such as readily to be mis- 

 taken for specific differences, which has actually been done again and again. The tail 

 of the male, for instance, is always much longer than that of the female ; the males 

 have sharp asperities between the joints of the hind legs ; moreover the color and 

 ornamentation differ considerably. As a genus, however, Cinosternum is easily 

 distinguished. Yet our common Mud-Turtle, (Ozotheca odorata,) has ))een referred 

 to Cinosternum by some authors, and to Sternotha^rus by others, until it was placed 

 in the genus Staurotypus by Dumeril and Bibron. Having formerly hud an oppor- 

 tunity of examining, in Munich, the type on which Wagler founded the genus Stauro- 

 typus, I can affirm that our species is by no means generically identical with Wag- 

 ler's Staurotypus, and still less belongs to Bell's Sternothairus, or to Spix's Cinoster- 

 num. It constitutes, indeed, a genus for itself, which I have called Ozotheca, the 

 characters of which are intermediate between those of Staurotypus and those of 

 Cinosternum. There are, in the southern parts of our country, other sjiecies of this 

 genus, as I have had good opportunity of ascertaining, but I have no hesitation in 

 saying that the characters according to which some of the species now admitted 

 have been established in this family by Wagler, Dumeril and Bibron, Gray, and 

 LeConte, may all be found upon specimens of different age, sex, and size, living 

 together in the same pond in our Northern States, so that the true differences 

 of our species are still to be pointed out. 



All herpetologists seem to agree about the limits of the genera Emys and Cis- 

 tudo, though they differ about the name, Canino retaining the name of Terrapene 

 for the group to which Dumeril and Bibron assign the name of Emys, and giving 

 the name of Emys to that group which Dumeril and Bibron call Cistudo, and which 

 Gray farther subdivides into Cistudo proper and Lutremj's. The descriptions of our 

 species below will show that the distinction introduced by Gray is truly founded, and 

 that Cistudo and Lutremys are not only sub-genera, but constitute entirely distinct 

 genera belonging even to different sub-families. As the name Cistudo was first assigned 

 to the Cistudo Carolina, it is proper it should retain it, AvhUe it is eiiually proper 

 that the group to which Gray assigns the name Lutrem}s should be called Emys, 

 as it includes the European Emys, upon which the genus Emys was founded by Bron- 

 gniart. More than twenty years ago, Canino had already called tiu' attention of 

 herpetologi.sts to this point, and set it all right ; yet no one has followed his sug- 

 gestion, thus fiir. Accordingly, there exists in North America not a single Emys, 

 properly speaking, among those which have been described under that generic name. 

 Moreover, the species which have been referred to that genus do not. by any means, 

 all belong to one and the same genu.s. 



