1864.] DR. J. E. GRAY ON THE TRIONYCHID&. 81 
A. Skull solid, subtrigonal ; nose moderate ; eyes lateral; forehead 
short, not longer than the face ; palate concave, with a well- 
raised alveolar ridge, and a deep pit before and behind the in- 
ternal nostrils. Trionychina. 
a. Lower jaw (of adult) with a broad, flat alveolar disk ; palate with 
a deep, wide concavity in front of the inner nostrils. 
TRIONYX. 
Skull oblong, swollen. Nose convex, arched. Forehead convex. 
Upper jaw with a broad, flat, rugose alveolar plate, which is narrow in 
front and wide behind. Lower jaw with a broad, deeply concave 
alveolar edge, which is of nearly equal width in all parts, and witha 
slight prominence in the middle of the hinder edge. Palate with a 
broad, deep concavity, which is nearly as wide before as behind, and 
with the large oblong internal nostrils in the hinder part of the palate, 
and a deep groove, separated by a longitudinal ridge, behind each 
of them. Sternal callosities four, well developed. 
“The nostrils rather small, far apart, with a lobe on the inner 
side. Pupil cireular.”’—Wagler. 
TRIONYX GANGETICUS, Cuvier, R. A. ii. 16; Gray, Cat. Shield 
Rept. in B.M. 66. 
Aspidonectes indicus, Fitz. 
Aspidonectes gangeticus, Wagler, N. Syst. Amph. t. 2. f. 13-18 
& f. 20. ° 
Hab. India: Ganges. 
Cuvier figured the skull (Oss. Fos. v. 187, t.11. f. 5-8); and it 
is also figured in the ‘Cat. of Shield Rept. in B.M.’ (t. 42. f. 1). 
Wagler figured some part of the skeleton (N. Syst. Amph. t. 2. 
f. 13-18 & f. 20). 
RAFETUS.- 
Skull oblong, swollen. Nose convex, arched. Forehead flat. 
Upper jaw with rather broad rugose alveolar plates, rather wider 
behind than in front. Lower jaw with a broad, slightly concave 
alveolar edge, which is rather wider in front. Palate concave, with 
a broad, deep concavity, which is rather narrower in front than be- 
hind, and with the large oblong internal nostrils in the hinder part of 
the palate, and a deep groove, separated by a central longitudinal 
ridge, behind each of them. Sternal callosities two, lateral, small. 
The skull of this genus is very similar to that of the genus Trionya, 
as restricted in this paper; but it is at once known from that genus 
by the absence of the hinder sternal callosities and the small size of 
the lateral ones. 
RAFETUS EUPHRATICUS. 
Trionyx rafeht, Gray, Cat. Shield Rept. B.M. 65. t. 30. 
Tyrse rafeht, Gray, Cat. Tort. B.M. 49. 
Proc. Zoou. Soc.—1864, No. VI. 
