SIWALIK AND NARBADA CHELONIA. 
49—203 
ranging down to the lower eocene of Europe/ and the eocene (Bridger beds) of 
North America.- The foregoing observations will, however, have shown that since 
these species are mainly, or entirely, founded upon the carapace, or fragments of the 
same, it cannot be determined whether some of them may not have belonged to 
Chitra or Peloehelys. 
Indian and Burmese species. — Of the existing Indian and Burmese forms Mr. 
Theobald^ recognizes the following three species from India proper, viz.: — 
Trionyx gangeticus, Cuvier. Facial part of cranium short ; plastral callosities well 
developed. 
Trionyx sewaare, Gray {ex B. Hamilton, MS.). Facial part of cranium short : 
plastral characters of adult unknown. As far as is known this species can only be 
distinguished from the last by its colouration. 
Trionyx ocellatus, Gray. Facial portion of cranium more elongate. Sculpture on 
the callosities coarser than in T. gangeticus, and the lateral scutes more bent. 
From the districts to the east of the Bay of Bengal the following five species 
are recognized, viz.: — 
Trionyx phayrei,^ Theobald. Cranium resembling that of T. gangeticus ; plastron 
imperfectly ossified, callosities being absent in the young : the carapace has an 
indistinct median keel. 
Trionyx stellatus, Schlegel. Facial portion of cranium elongate ; plastron 
imperfectly ossified in the young. 
Trionyx peguensis, Gray. Described only from the skull. 
Trionyx grayi, Theobald. Cranium agrees with that of the latter in general 
characters, but differs in colouration. 
Trionyx ephippium, Theobald. Only known by the young, in which the plastral 
callosities are absent. 
Apparently, as far as is known, the nuchal scute is fully ossified in all these 
forms, and is rugose on the whole of the dorsal aspect. Tliere is, however, another 
Asiatic group,® in which the nuchal scute (at least in the young) is not fully ossified 
posteriorly, and is frequently only partially rugose. Examples of this group are T. 
guentherP (Gray), of which the habitat is unknown ; T. subplanus, Schweigg, of 
Singapore, etc.; and T. ornatus,'^ of Borneo. 
Siwalik forms. — The earliest record of the occurrence of Trionyx (or one of the 
allied genera) in the Siwaliks is by Clift,® who figured some fragments of shells 
obtained from Burma, among which are, however, included some specimens 
apparently belonging to Emyda. The occmTence of similar remains both in Burma 
and the Siwalik Hills was noted by Falconer® in 1831, and mention of the genus is 
also made in his notes.“ In his ‘ Catalogue of the Fossil Vertebrata in the Museum 
1 Vide Owen and Bell, “ Fossil Eeptilia of the London Clay, etc.,” pt. I. pp. 45-61 (1849). 
2 Vide Leidy, “ Extinct Vertebrate Fauna of the Western Territories,” pp. 341-342 (1873). 
3 ‘ Proc. As. Soc. Beng.,’ 1875, p. 178. “ Catalogue of the Keptiles of British India,” pp. 340-341. 
4 Syn. T. cariniferus, Gray {non Aspilus cariniferus, Gray). 
5 Comprehending the genera Aspilus and Bogania of Gray. 
6 Vide Gunther, ‘‘ Eeptiles of British India,” pi. VI. fig. A. 7 Ibid, fig. B. 
6 ‘ Trans. Geol. Soc.’ ser. 2. vol. II. pp. 374-375 (1828). 
9 ]'ide “ Falconer’s Palaeontological Memoirs;” vol. I. p. 413. 10 Ibid, pp. 23, 35, 39. 
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