246 TRIONYCHID A. 
nuchal border of dorsal disk without 
conical tubercles; a light black-edged 
streak on each side of the head, uniting 
with its fellow into a large triangular 
marking extending from between the 
eyes to the end of the proboscis .... 12. emoryi, p. 258. 
Snout a little longer than the diameter 
of the orbit; nuchal border of dorsal 
disk with conical spine-like tubercles ; 
light head-streaks uniting on the 
snout, in front of the orbits ........ 13. ferox, p. 259. 
Snout a little longer than the diameter of 
the orbit ; nuchal border of dorsal disk 
with conical spine-like tubercles ; light 
head-streaks uniting on the end of the 
snout, at the base of the proboscis .. 14. spinifer, p. 259. 
Snout very narrow and pointed; nuchal 
border of dorsal disk without conical 
HUDeY cles aetanie coe sm toto eek eor en 15. muticus, p. 260. 
1, Trionyx subplanus. 
Trionyx subplanus, Geoff. Ann. Mus. xiv. p. 11, pl. v. fig. 2 (1809) ; 
Gray, Ill. Ind. Zool. 1. pl. Ixxix. (1832) ; Grinth. Rept. Brit. Ind. 
p- 49 (1864) ; Strauch, Verth. Schildkr. p. 180 (1865). 
Gymnopus subplanus, Dum. § Bibr. ii. p. 496 (1835). 
Dogania subplana, Gray, Cat. Tort. p. 49 (1844), and Sh, Rept. i. 
p. 69, pl. xxxiii, (1855), and Proc. Zool. Soc. 1862, p. 265, and 
SEA a Sh. Rept. i. p. 106 (1870), and Proc. Zool. Soe. 1873, 
. O7, fig. 
Titonve frenatus, Gray, Cat. Sh. Rept. i. p. 67. 
Dogania giintheri, Gray, Proc. Zool. Soc. 1862, p. 265, and Suppl. 
Cat. Sh. Rept. i. p. 107, and Proc. Zool. Soc. 1873, p. 58. 
Trionyx giintheri, Giinth. Rept. Brit. Ind. p. 49, pl. vi. fig. A. 
Potamochelys ? frenatus, Gray, Proc. Zool. Soc, 1864, p. 87. 
Sarbieria frenata, Gray, Proc. Zool. Soc. 1869, p. 220, and Suppl. Cat. 
Sh. Rept. i. p. 100. 
Platypeltis ferox, part., Gray, Proc. Zool. Soc. 1873, p. 58. 
Trionyx ? dillwynii, Gray, Ann. § Mag. N. H, (4) xi. p. 806 (1878). 
Carapace very flat; costal plates eight pairs, the last well deve- 
loped and separated by the last neural plate; a single neural be- 
tween the first pair of costals; these plates very finely granulate and 
vermiculate ; a large fontanelle, till late in life, between the nuchal 
and dorsal plates. Epiplastra narrowly separated from each other 
in front of the entoplastron, which forms an obtuse or a right angle ; 
plastral rugosities scarcely developed, on the hyo- and hypoplastra 
and on the xiphiplastra. Dorsal skin of young with interrupted 
longitudinal ridges. Head very large ; snout (on the skull) about 
as long as the diameter of the orbit, which is more than double the 
interorbital width; postorbital arch extremely narrow, forming a 
