imiM TERTIARY & POST-TERTIARY VERTEBRATA. 
SIWALIK CROCODILIA, LACERTILIA, & OPHIDIA. 
By R. LYDEKKER, B.A., F.a.S., etc. 
(WITH PLATES XXVIII. TO XXXY.) 
INTRODUCTORY. 
Previous literature. — As was the case with the Chelonia till the publication of the 
preceding part of this volume, the Siwalik Crocodilia have been hitherto but very 
imperfectly known. Two memoirs were published by Cautley, which will be noticed 
in the sequel, and some illustrations, which are in several instances incorrectly named, 
are given in “Falconer’s Palseontological Memoirs”; but beyond this nothing of 
any importance has been hitherto published. The few notes left by Falconer are 
manifestly crude, and were not meant to have seen the light in their present form. 
The single known lacertian bone has been figured in the work cited ; while a brief 
notice of ophidian vertebrae has been previously published by the present writer. 
Relation of the fossil and existing Indian .Crocodilia . — ^^The crocodilian fauna of the 
Siwaliks as a whole considerably exceeded that of modern India, both in the number 
of species and the dimensions which some of those species attained, and is thus in 
harmony with the relations of the pliocene to the existing mammalian fauna. This 
excess is, however, not equally distributed in all groups, since while in India there 
are at the present day three species of Crocodilus and one of Gharialis, in the Siwalik 
epoch there were but two species of the former, while there were no less than six 
species belonging to the gharialoid group, of which five are referred to the existing 
genus, and the sixth is made the type of a new genus. Even, however, in 
the genus Crocodilus there is in one sense an excess of the fossil over the recent forms 
if we eliminate from the latter the two allied species G. porosus and 0. pondicherianus^ 
which the fossil evidence indicates are probably immigrants into India from the 
A 
