208 DR. J. E. GRAY ON THE TORTOISES. [ Mar. 11, 
surface broad, divided just over the internal nostrils by a large, 
thick central ridge parallel with the outer side, having a broad 
space on each side of it. Lower jaw strong, rather short, front and 
sides convex and rounded beneath; alveolar surface broad, with 
a short outer edge of an irregular narrow subcentral ridge parallel 
with the outer margin. 
21. DeRMATEMYS. 
Dermatemys, Gray, Cat. Shield Reptiles in B. M. p. 49. 
Skull figured by M. Aug. Duméril in the ‘ Archives du Muséum,’ 
vi. p. 223, t. 15. ‘The alveolar surfaces are broad, with distinct 
dentated ridges, like those of the genera Pseudemys and Batagur.” 
Gray, P. Z. 8. 1864. 
This genus was arranged, in the ‘ Catalogue of Shield Reptiles,’ 
in the Chelydradea, near Chelydra, on account of the additional 
shield on the suture; but at that time the thorax only was known. 
The animal, like the skull, is very like Pseudemys and Batagur. 
The specimen in spirit of the animal in the British Museum, re- 
ceived from Mr. Salvin, has very small gular shields, for the greater 
part of their length united, which gives them much the appearance 
of a single shield. This union and their small size give the animal 
at first sight the appearance of an Hydraspis, the gular shields being 
regarded as the intergular of that genus. 
Fam. [V. PLatysTERNID. 
Head very large, covered with a thick, hard, bony case; upper 
jaw with a strong short-edged central hook. Skull thick, hard ; 
zygomatic arch much dilated posteriorly and forming a bony cover- 
ing over the temporal muscles. Toes 5.4, short, free at the ends ; 
the three middle ones of the fore foot and the two middle ones of 
the hind foot longest; claws compressed, acute. Tail cylindrical, 
elongated, covered with rings of square shields. ‘Thorax thin. Ster- 
num solid, broad, attached to the thorax by a bony extension co- 
vered with the ends of the pectoral and abdominal plates; not 
transversely divided, separated from the marginal shields by a longi- 
tudinal series of small shields. 
Emydide, b, Gray, Cat. Shield Reptiles, p. 49. 
Emydide, § B, Gray, Cat. Tortoises in B. M. p. 13. 
PLATYSTERNON. 
Platysternon, Gray, Cat. Shield Rept. p. 49. 
Fam. CHELYDID2. 
In the ‘ Proceedings’ of the Society for 1864, p. 128, I proposed 
an arrangement of the genera of this family founded on the exami- 
nation of the skull of the genera which I then knew, and I figured 
some of them. 
