204—50 INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
of the Asiatic Society of Bengal,”^ he again records the occurrence of the genus in 
the Siwaliks of Burma. 
Fragments of the carapace and plastron of Trionyx and its allies are of 
exceedingly common occurrence throughout the Siwaliks of India and Burma, and 
strongly marked differences in the form of the sculpture of different specimens 
indicate the occurrence of several distinct species. The imperfect state of our 
knowledge of the existing species of India and Burma (and still more of those of 
other parts of Asia) shows, however, that it would be worse than useless to attempt 
the specific (or even generic) identification of many such specimens. Even 
with nearly complete fossil specimens of the shell it would in many cases be 
impossible to determine at present whether they were distinct from or identical with 
living species ; and accordingly in the two Siwalik specimens noticed below under 
the head of the present genus the writer has not attempted a specific determination. 
A. Nuchal scute suturally connected with the first costal. 
Species 1. Trionyx gangeticus, Cuvier.^ 
(For yalceontological purposes it is obvious that this species must he taken to include T. 
sewaare, as that form is only distinguished by its colouration.) 
Earlier notice of reputed oceurrence in the pleistocene. — In 1870 Stoliczka® described 
and figured two fragments of the plastron of a large Trionyx from the pleistocene of 
the Narbada valley, which he considered might very probably be referred to the 
present species. It is, however, by no means clear that they might not have belonged 
to T. ocellatus, as they exhibit a very coarse sculpture. 
Cranium . — The cranium of a large Trionyx represented of three-fourths the 
natural size in plate XXV. figs. 3. 3a. 3b., was obtained by Mr. C. Fraser from the 
pleistocene of the Narbada valley, and presented by him to the British Museum 
sometime previously to 1843. With the exception of the loss of the occipital 
condyle, of the long supraoccipital projection, and of the parallel lateral projections, 
the specimen is almost perfect. It is precisely similar to the cranium of the existing 
T. gangeticus,^ exhibiting very clearly the short facial portion which marks its 
distinction from 21 ocellatus. It is unfortunate that the mandible is not preserved 
(by which the skull of T. gangeticus is at once distinguished from that of the Burmese 
T. phayrefi), but since the present specimen cannot possibly be distinguished, from 
the cranium of the former species, and it is improbable that the latter occurred in 
the pleistocene of the western side of India, no reasonable doubt can be entertained 
that it indicates the existence of T. gangeticus in the Narbada pleistocene. 
Distribution. — According to Mr. Theobald® the existing form inhabits the Ganges 
valley from Bengal to the North-West Provinces. The trionyches of the Narbada 
1 Pages 32, 33 (1852). The genus Trionyx is taken to include Trionyx proper [=Gyninopus), and Emyda [=Cryptopus) . 
2 “ Eegne Animal,” '2nd ed. vol. II. p. 16 (1829). For the synonomy see Theobald, ‘ Proc. As. Soc. Beng.’ 1875, p. 171. 
3 ‘ Eec. Geol. Surv. Ind.’ vol. II. p. 39. pi. I. figs. 4, 5. 
4 Compare Gray, “ Catalogue of Shield-Reptiles,” pt, I. pi. XLII. fig. 1. 5 Vide Theobald, op. cit., p. 178. 
6 Catalogue of the Reptiles of British India,” p. 29. 
/ 
