183 Dr, J. E. Gray on American Emydidse. 



markably in its colour and sculpture^ as well as in the size of 

 the head," — all characters used to separate other species of 

 Terrapins. 



E. areolata, Dum. (Arch. Mus. vi. 223, 1. 14), is also regarded 

 as a variety from Central America. 



PsEUDEMYs, Gray, Proc. Zool. Soc. 1855, 197; Cat. Shield Rept. 

 35 {\mb).=Ptychemys, Agassiz, Contrib. i. 431 (1857). 

 Nectemys, Agassiz, Contrib. ii. 642 (1857). 



1. P. concinna, Gray, Cat. /. c. 34. Ptychemys concinna, Agass. 

 Contrib. i. 432, 1. 1. f. 13, t. 2. f. 4-6 (adult). Emys flori- 

 dana, Holbrook, t. 8 (mc?e Agassiz). 



2. P. hieroglyphica, Gray, /. c. 34. Emys h., Holbrook, 1. 17. 



3. P. mobilensis. Ptychemys mobilensis, Agassiz, Contrib. 433, 

 t. 3. f. 14, 16. E. mobilensis, Holbrook, t. 9. E. ventricosa, 

 Gray, Cat. /. c. 28 ? 



4. P. serrata, Gray, /. c. 34. Ptychemys rugosa, Agassiz, Con- 

 trib. 431, t. 26. f. 1, 11, t. 27. f. 1-3. E. rubriventris, Hol- 

 brook, t. 6. E. rivulata, Gray, Cat. t. 11 {vide Agassiz). 



5. Pseudemys decussata. Emys decussata, Bell, Test. 1. 1 ; Gray, 

 Cat. /. c. 20. Ptychemys decussata, Agassiz, Contrib. i. 431. 



6. Pseudemys ? Berardi. Emys Berardi, Dum. & Bibr. Emys 

 D' Orbignyii, Dum. & Bibr. Erp. Gen. ; D^Orb. Voy. 

 Amer. Merid. Rept. t. 1, from Buenos Ayres. Probably 

 belonging to this genus, from the distribution of the colour ; 

 but it is peculiar for having a pale margin to the dark ster- 

 num, like Rhinoclemys. 



I am by no means satisfied that these species are well deter- 

 mined, that the extent of the notching and dentation of the 

 beak is a character of the importance that is attached to it, or 

 that when the pattern of the coloration and the changes that 

 each presents have been more carefully studied, they will not 

 afford better characters than those now used. The nuchal 

 shield, as in Calliclemys, is often marked with a central streak. 



Rhinoclemys, Fitzinger, = Emys ftt^ Gray, Cat. Shield Rept. 

 31 (1855), of Tropical America. Peculiar for being of a 

 dark, nearly uniform colour, with a pale ring round the cir- 

 cumference of the dark sternum. 



Some species have the keel of the shell of the same colour as 

 the back -, and the head is dark, with a streak on each side of 

 the nose and temple. The toes are very short, with a short 

 web. 



1. Rhinoclemys scabra. Emys scabra. Gray, Cat. /. c. 31, and 



