262 



XRIONYClODiE. 



adult, with a callosity ; each epiplastron likewise with a callosity, 

 which is, however, very minute. Erown above, whitish inforioiiy ; 

 head without markings ; back blotched with darker brown. 



The length of the dorsal disk does not exceed 2b centim. 



Mississippi, Ohio, and tsaint Lawrence. 



? * (Type of Callinia microcephala.) 



u. Hgr., stfl'd., skull separate. 



2. PELOCHELYS. 



Chitra, part., Gray, Cat. Sh. Rept. i. p. 70 (1855) ; Gilnth. Bepi. 



Brit. Iml. p. 50 (1864). 

 Pelochelys, Gray, Proc. Zool. Soc. 1864, p. 89, and Siq)pl. Cat. Sh. 



Bept. i. p. 90 (1870), and Proc. Zool. Soc. 1873, p. 40. 



Outer extremities of the nuchal plate overlying the second dorsal 

 rib ; neural plates well developed. Limbs completely exposed. 

 Hyoplastron distinct from hypoplastron ; not more than five plastral 



Fig. 69. 



Skull of Idochelys cantoris. ^{From Graj-, P. Z. 6 1664.) 



callosities. Bony choanaj between the orbits; jaws weak; post- 

 orbital arch as broad as the diameter of the orbit ; pterygoids 

 posterior border free, without ascending process. 

 East Indies. 



* The specimen, stated to have been obtained by Mr. Wallace at Sarawak, 

 was purchased at Stevens's sales. 



