SIWALIK AND NARBADA CHELONIA. 
53—207 
adult of which the nuchal scute is entirely unsculptured, and has an unossitied space 
between it and the 1st costal. 
Although the evidence of such small fragments perhaps makes it inadvisable to 
assign a distinct specific name, yet it is most probable that the present specimens 
indicate a new species, which may be regarded as an ancestral form closely related 
to Trionyx guentheri^ but with a still more generalized structure. It is a very 
remarkable fact that while we have evidence of this less specialized form in the 
Siwaliks of India, and of kindred living Asiatic species, yet that all the known 
species from the English eocene^ exhibit as full a development of the nuchal scute as 
in the existing T. gangeticus ; thus showing that the origin of the group is to be 
looked for in much earlier geological periods, and that the fossil and living Asiatic 
forms with imperfectly developed nuchal and 1st costal scutes should probably be 
regarded as survivals of a primitive type. 
Distribution . — Assuming that both the specimens noticed above belong to the 
same species, they indicate that the range of the latter in time extended from the 
lower to the upper Siwaliks, and in space from Sind to the Punjab ; both the latter 
areas being in the Indus basin. 
Genus III. CHITRA, Gray.^ 
The characters of this genus have been alluded to under the head of Trionyx : 
the only known species is G. indica. The nuchal scute is fully ossified, and entirely 
rugose. 
Species. Chitra indica. Gray.® 
Syn. Trionyx indicus, Gray.^ 
Carapace. — The British Museum possesses two portions of the carapace of a 
very large species of triony chine tortoise from the Siwalik Hills, which are figured 
of one-fourth the natural size in plate XXVII. figs. 1 and 2. Both specimens belong 
to subadult individuals, as is shown by the extension of the costal scutes nearly up 
to the free extremities of the ribs. The first specimen (fig. 1) exhibits the nuchal, 
and the complete 1st and parts of the 2nd vertebral and costal scutes ; while the 
second shows the greater part of the first six vertebral and- costal scutes, and from 
the identity in size and form between the first two of these and the corresponding 
scutes of the first specimen, there can be no doubt as to the specific unity of the two 
specimens. 
The first specimen exhibits on its ventral aspect the anterior elements of the 
plastron, and since the entoplastral portion shows not the slightest trace of an 
azygos callosity, the present form differs from the existing Indian species of Trionyx ; 
and as it is of considerably larger size than Pelochelys cantori (in which an azygos 
1 Vide Owen and Bell, “ Fossil Eeptilia of tlie London Clay, etc.” part I. ((1849). 
2 “ Catalogue of Tortoises in the British Museum,” p. 49 (1844). 
3 “ Synopsis lloptiliuin,” p. 47 (1831 ). Trimijx. l.oc.cU. 
N 
