1. TRIONTX. 251 



Nilssonia formosa, part., Gray, Proc. Zool, Sue. 1873, p. 40. 

 Isola pepuonsis, Orai/, I. c. p. 51, figs. 



Trionvx grayii, Theob. Proc. As. Sue. Bern/. 1875, p. 17G, pi. iii., and 

 Cat. liept. Brit. Iml. p. 31. 



Costal plates eight pairs, the last well developed and in contact 

 throughout on the median Hno ; 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 caUositios well developed, hyo-hypoplastral 

 and xiphiplastral, and coarsely sculptured like the carapace. Head 

 moderate ; snout (on the skuU) 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 vrith 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 T. hurum. 



Size of T. hurum. 



Burma. 



a. Yg., spir., skuU separate, Pegu. W. Theobald, Esq. [C.]. 



mandible lost. (T-sq^e.) 



b. Head, spir., skull separate. Pegu. W. Theobald, Esq. [C.]. 



(Type of T.pejinensis.) 



c. Hgr., skull & shell. Thayet-Myo, W. Theobald, Esq. [E,]. 



Irawaddv. (Type of T. gruxji.) 



d. Yg., skull. Burma. ' W. Theobald, Esq. [E.]. 



6. Trionyx phayrii. 



Trionyx phayrei, Theob. Journ. Linn. Soc. x. p. 18 (1868) ; Anders. 



Proc. Zool. Soe. 1871, p. 154; Theob. Proc. As. Soc. Benff. 1875, 



p. 175, a7id Cat. Eept. Brit. Ind. p. 30 (187G). 

 jeudi, Crraij, Proc. Zool. Soc. 18G9, p. 217, figs., and Stippl. Cat. 



Sh. Rept. i. p. 97 (1870), aiid yinn. S)- Mag. N. II. (4j x. p. 330 



(1872), and Proc. Zool. Soc. 1873, p. 49. 



cariniferus (non Gray), Theob. Proc. As. Soc. Beng. 1874, p. 80, 



pi. 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 T. formosus, but snout a 

 little longer in the adult. Head of adult spotted or vermiculated 

 with black above and uniform whitish inferiorly, as in T. formosus. 



