1, TRIONYX. 951 
Nilssonia formosa, part., Gray, Proc. Zool, Soe. 1873, p. 46. 
Isola peguensis, Gray, J. c. p. 51, figs. 
Trionyx grayii, Theob. Proc. As. Soc, Beng. 1875, p. 176, pl. iii., and 
Cat. Rept. Brit. Ind. p. 31. 
Costal plates eight pairs, the last well developed and in contact 
throughout on the median line; a single neural between the first 
pair of costals ; plates coarsely pitted and vermiculate. Dorsal skin 
of young with longitudinal ridges of small tubercles. Epiplastra 
separated from each other; entoplastron forming an obtuse or 
straight angle; plastral callosities well developed, hyo-hypoplastral 
and xiphiplastral, and coarsely sculptured like the carapace. Head 
moderate ; snout (on the skull) about as long as the diameter of 
the orbit ; interorbital region, in the adult, as broad as the nasal 
fossa ; postorbital arch, in the adult, a little less than half the 
diameter of the orbit; mandible with a strong ridge along the 
symphysis, the diameter of which equals or a little exceeds that 
of the orbit. Olive-brown above, white below; head of young 
ornamented with yellow black-edged markings, the largest being 
a cross band on each side of the back of the head ; these markings 
disappear in the adult, the head of which is closely spotted with 
black above and uniform white inferiorly ; young with four large 
dorsal ocelli, as in 7’. hurum. 
Size of 7. hurum. 
Burma. 
a. Yg., spir., skull separate, Pegu. W. Theobald, Esq. [C.]. 
mandible lost. (Type.) 
b, Head, spir., skull separate. Peou. W. Theobald, Esq. [C.}. 
(Type of 7. pequensis.) 
e. Her., skull & shell. Thayet-Myo, W. Theobald, Ksq. [E.]. 
Trawaddy. (Type of 7. grayt.) 
d. Ye., skull, Burma. W, Theobald, Esq. [ E. ]. 
6. Trionyx phayrii. 
Trionyx phayrei, Theob. Journ. Linn. Soc. x. p. 18 (1868); Anders, 
Proc. Zool. Soc, 1871, p. 154; Theob. Proc. As. Soc, Beng. 1875, 
p- 175, and Cat. Rept. Brit. Ind. p. 30 (1876). 
jeudi, Gray, Proc. Zool. Soc, 1869, p. 217, figs., and Suppl. Cat. 
Sh. Rept. i. p. 97 (1870), and Ann. § Mag. N. H. (4) x. p. 83 
(1872), and Proc. Zool. Soc. 1873, p. 49. 
cariniferus (non Gray), Theob. Proc. As. Soc. Beng. 1874, p. 80, 
pl. iv. 
Costal plates eight pairs, the last well developed, with slightly 
concave posterior border, and in contact on the median line; a 
single neural between the first pair of costals ; plates rather coarsely 
pitted and vermiculate. Epiplastra in contact in front of the ento- 
plastron, which forms an obtuse or straight angle; plastral callo- 
sities hardly developed, the hyoplastra bearing a mere trace of 
sculpture. Head moderate; skull as in 7. formosus, but snout a 
little longer in the adult. Head of adult spotted or vermiculated 
with black above and uniform whitish inferiorly, as in 7’. formosus. 
