210—2 INDIAN TERTIAEY AND POST-TERTIARY VERTEBRATA. 
eastward. One of the two Siwalik species of Grocodilus is evidently the ancestral 
form of the existing G. palustris, and it has been a question whether the fossil should 
be regarded as specifically distinct, or merely as a race of that species : in con- 
formity, however, with the course pursued in the analogous instances among the 
Chelonia the former view has been adopted. In the genus Oharialis one form has 
been regarded as specifically identical with the existing 0. gangeticus, while all the 
others are totally distinct, and several of them differ very widely from that species. 
Two members of the gharialoid group indicate crocodilians of larger size than have 
been hitherto described from any part of the world, and formed worthy consorts in 
point of size with Colossochelys atlas. Nothing is at present known of the crocodiles 
of the pleistocene Narbada beds. As the Lacertilia and Ophidia are known merely 
by two species, nothing can be predicated of their relations to the existing fauna, 
with the exception that the one species of Varanus largely exceeded all its living 
congeners in point of size. 
« 
Order. CROCODILIA. 
Suborder. EUSUCHIA. 
Family. GBO CODILIDJE. 
Generic divisions . — The existing and Siwalik crocodilians, all of which it seems 
advisable to include in a single family, may be divided from the characters of the 
skull as follows, vis .: — 
A. Alligatoroid group. Both the first and fourth mandibular teeth received into pits, or per- 
forations, in the cranium ; the maxillary teeth biting on the outer side of the smaller mandibular 
teeth. 
a. Alligator. Nasals dividing the anterior nares. \ The writer is inclined to think that all 
b. Caiman. Supratemporal fossae obliterated. > the genera might well be included in 
c. Jacare. Vomers appearing on the palate. / Alligator. 
B. SucHOiD GROUP. The first mandibular tooth received into a pit or perforation, the fourth into 
a lateral notch in the cranium ; the nasals articulate with the premaxillae ; mandibular and 
maxillary teeth interlocking. 
a. Crocodilus?- 
C. Gharialoid group. Skull elongated into a rostrum ; splenials enter into mandibular symphysis. 
1. Both the first and fourth mandibular teeth received into lateral notches in the cranium ; 
maxillary and mandibular teeth interlocking. 
a. Tomistoma? Mandibular symphysis extends to the fifteenth tooth ; premaxillae hardly expanded, 
and articulating with nasals. 
h. Gharialis. Mandibular symphysis extends to the twenty-third or twenty-fourth tooth® ; pre- 
maxillae and extremity of mandible much expanded® ; nasals widely separated from pre- 
maxillae. 
2. First mandibular tooth received into a lateral notch, fourth into a pit in the cranium ; maxillary 
teeth biting outside the mandibular. 
a. No living representative. 
1 The African C. cataphraetus is sometimes separated as Mecistops. 
2 Syn. Rhynchosuehus, Huxley. 
3 These characters are not applicable to some of the fossil forms. 
