SIWALIK AND NARBADA CHELONIA. 
51—205 
river appear, however, to be totally unknown, so that there seems no reason why the 
species should not still inhabit that valley. 
Teionyx, sp. 2. 
Shell . — In plate XXVII. fig. 3. there is represented of one-half the natural size 
the right half of the ventral aspect of the shell of a small Trionyx from the Siwalik 
Hills ; a portion of the dorsal aspect of the carapace being represented in fig. 3a of 
the same plate. The specimen is now in the Indian Museum, and was obtained by 
exchange with the Museum of Comparative Anatomy at Cambridge, having been 
purchased by the latter institution among a small collection of Siwalik fossils : the 
matrix leaves no doubt of the correctness of the locality. 
The condition of the plastron and of the costal scutes of the carapace indicates 
that the specimen belonged to a fully adult individual ; and the length of the 
carapace when complete was probably about 12 inches. On the ventral aspect the 
whole of the plastral elements, with the exception of the epiplastra, are exhibited in 
a perfect condition, but the carapace is considerably damaged. 
There is a well-marked azygos (entoplastral) callosity on the plastron; the 
paired callosities being fully ossified, and uniting in the middle line ; the sculpture 
is somewhat finer than in T. gangeticus. The carapace does not show the form of 
the liuchal or vertebral scutes; but it exhibits three very well-marked continuous 
longitudinal keels, and there is no median depression. 
Affinities. — The presence of an azygos plastral callosity, as well as its greatly 
inferior size, differentiates the present specimen from Chitra indica. Pelochelys cantori 
is also considerably larger, and differs in the form of the paired plastral callosities ; 
the specimens in the British Museum not. showing the distinctly tricarinate carapace 
of the fossil. 
The fossil agrees with the Indian species of Trionyx in the possession of an 
azygos plastral callosity ; but apparently differs from all in which the adult carapace 
is known by the presence of the three distinct keels on the carapace.^ In addition 
to this character T. gangeticus and the two allied Indian species are distinguished by 
their greatly superior dimensions and coarser plastral sculpture. Nothing can be 
predicated as to the relations of the fossil with T. peguensis, T. grayi, and T. 
ephippimn. 
In T. mgijptiacus., Geoffr., there is a larger azygos plastral callosity than in the 
present specimen, and that species attains a considerably greater size, but specimens 
in the British Museum show a similarly tricarinate carapace. 
B. Nuchal scute mot suturally connected with the first costal. 
Teionyx, sp. 3. 
First costal scute. — This second Siwalik species is indicated by ’the specimen 
1 In T. phayrei {=T. eariniferus, Gray) there is a vertebral keel on the carapace, but no costal keels. The species is 
much larger than the present form, equalling in size T. yanyeiicus. 
