212 DR. J. E. GRAY ON THE TORTOISES. [ Mar. 11, 
2. The front edge of the lower jaw narrow; the inner surface 
of the front part of the jaw shelving inwards. 
a. In some of these the hinder part of the sides of the edge 
is more or less expanded and flattened out into an alveolar 
disk: Dogania, Potamochelys, Cyclanosteus. 
- 6. In others the sides of the edge are as narrow as the front 
part: Tyrse, Platypeltis, Callinia. 
The genera of the family may be thus arranged :— 
Section I. The head ovate or oblong, face moderate. Skull strong, 
x 
or 
6. 
thick, solid. 
. The sternum contracted behind, without any flaps over the hind 
legs. 
. Nostrils small, far apart, on the sides of the end of the proboscis. 
. Amypa. A. mutica. 
. Nostrils moderate, circular, close together in the middle of the 
end of the proboscis, with a small lobe on the inner side. 
Head short, forehead convex. The front and sides of the lower 
jaw with a broad, expanded, flat or slightly concave alveolar 
surface. Anterior palatine groove deep. 
a. Sternal callosities six. 
. Lanpemanta. UL. irrorata. 
}. Sternal callosities four. 
. Trionyx. Head short, forehead convex. Anterior palatine 
groove broad, shallow. Alveolar surface of the lower jaw 
broad, as wide in front as on the sides, rather concave, with a 
central longitudinal ridge in front. Hab. Asia. T' gangetica. 
. Forp1a. Head short, forehead convex. Anterior palatine 
groove narrow, linear, deep. Alveolar surface of the lower jaw 
very broad, as wide in front as on the sides, flat, granular. 
Hab. Africa. F. africana. 
. SarsprertA. Head rather elongate. Anterior palatine gruove 
(in beak) narrow, deep, gradually becoming wider behind (in 
skull). Alveolar surface (of beak) in lower jaw regularly con- 
cave and smooth in front, and slightly concave on the sides. 
Odd anterior bone of dorsal disk free and smooth in the young 
specimens. S. frenata. 
y. Sternal eallosities two, lateral. 
Aspitus. Head oblong, elongate. Alveolar surface of the upper 
jaw wider behind ; of the lower jaw broad, rather wider in front 
