216—8 INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
tlie mandible of the existing species. 
Specific distinctness and affinities. — The extreme rugosity of the facial sculpture 
of the species under consideration, together with the narrower interorbital bar, at 
once indicates its specific distinctness from C. siamensis, and it therefore only remains 
to consider whether the differences noticed above are of sufficient importance to 
specifically distinguish it from C. palustris. These differences may be summarised 
as follows, vis . — 
1. The greater relative width of the interorbital bar. 
2. The greater relative length of the facial aspect of the premaxilla, and the consequent more 
backward position of the anterior nares. 
3. The inverted V-shape and greater backward extension of the maxillo-premaxillary suture on the 
palatal aspect. 
4. The greater rugosity of the facial sculpture, more especially on the premaxillae of the adult. 
5. The smaller development of the preorbital rugose nodosities. 
6. The wider nasals (only noticed in the young). 
Taken together the foregoing well-marked characters appear sufficient to distinguish 
the Siwalik crocodile from the typical form of the allied existing species. There is, 
however, a variety of the latter from Ceylon,^ which approaches the fossil in the 
character No. 3, and therefore tends to diminish the value of the differences ; but as 
the few examples of this variety seen by the writer do not present the other 
characteristic features of the fossil there are still good grounds for regarding the 
latter as specifically distinct,^ and the new name C. sivalensis is accordingly 
proposed. 
That C. sivalensis is the ancestral form of G. palustris there can be no reasonable 
doubt, and the Ceylon variety of the latter must apparently be regarded as one 
retaining traces of a closer affinity with the ancestral species than is the case with 
the typical race. The direction and position of the maxillo-premaxillary suture on 
the palate of G. sivalensis seems to indicate a less degree of specialization than that 
occurring in typical examples of G. palustris ; or, in other words, is less widely 
removed from the C. porosus and C. vulgaris type, which as being nearer to 
Gharialis is probably a more generalized one. It is, however, very remarkable that 
in the English middle eocene C. hastingsice^ the position of the above-mentioned 
suture is nearly the same as in the G. palustris group. This fact, together with the 
occurence of Gharialis in the same beds, may perhaps indicate that the origin of the 
latter group is to be traced to the English middle eocene species, which attained 
a comparatively high degree of specialization. The occurrence of the present and 
the next species in the upper tertiaries of India, and the apparent total absence in 
1 Vide Gray “ Supplement to the Catalogue of Shield-Eeptiles ” pt. 2. p. 11 (1872). 
2 The difficulty of deciding as to what should be considered specific and what merely varietal characters in the case of 
those Siwalik reptiles which are evidently the ancestors of existing Indian species has been already mentioned in the 
preceding part (p. 186). The view there adopted of regarding as specifically distinct any form which can be well 
distinguished from its living ally has been followed here. 
3 Vide Owen and Bell “ EeptUes of the London Clay, etc,” pt. 2 pi. VII. In this species the nasals do not reach the 
anterior nares. 
