CROCODILIA. 47 



gangeticus, Auct., and from the (pei'haps nominal) Gavialis tenuirostris, Cuv., in the 

 form and relative size of the teeth. The crown (figs. 6, 7) is less slender in the fossil 

 than in the existing Gavials, and less compressed, its transverse section being nearly 

 circular. There are two opposite principal ridges, but they are less marked than in 

 the existing Gavials ; and are placed more obliquely to the axis of the jaw, i. e., the 

 internal ridge is more forward, and the external one more backward, when the tooth 

 is in its place in the jaw. In the modern Gavial, the opposite ridges, besides being 

 more trenchant, are nearly in the same transverse line. The other longitudinal ridges 

 on the enamel of the fossil teeth, are more numerous, more prominent, and better 

 defined, than in the existing Gavials : the intermediate tracts of enamel present the 

 same fine wrinkles in the fossil as in the existing Gavials' teeth. 



The two chief portions of jaw (fig. 1, and figs. 4, 5) belong to two individuals of 

 different ages \ indicated by the difference in the breadth and depth of the ramus : 

 both specimens being from the corresponding part of the jaw, viz. where it forms the 

 long symphysis characteristic of the Gavials. The specimen (figs. 4, 5) includes a 

 larger proportion of the jaw than the fragment delineated in fig. 1. 



On comparing the latter fragment of the fossil lower jaw with a specimen of a 

 lower jaw of the Gavialis gangeticus of the same breadth across the symphysial part, 

 at the intervals of the sockets, which breadth is 3 centimeters (1 inch 3 lines), I find 

 that the longitudinal extent of 10 centimeters (near 4 inches) of a ramus of the fossil 

 jaw includes five sockets ; but in the recent Gavial the same extent of jaw includes 

 seven sockets, showing that the teeth are fewer as well as larger in the fossil Gavial, in 

 proportion to the breadth of the jaws. 



The second portion of the jaw (fig. 2) is from the part where the rami diverge 

 posteriorly from the symphysis, and near the posterior termination of the dentary 

 series. Here the teeth become shorter in proportion to their thickness, and somewhat 

 closer placed together : there is a shallow depression (c) in each interspace of the 

 teeth, for the reception of the crowns of the opposite teeth when the mouth is shut. 

 These depressions are longer, deeper, and better defined in the fossil than in the recent 

 Gavial of the same size. 



The fragments of jaw and teeth of the fossil Gavial of Bracklesham show examples 

 of young teeth penetrating the base of the old ones, according to the law of succession 

 and shedding of the teeth, which characterises the existing Crocodilia : fig. 2 shows the 

 apex of one of the successional teeth at d ; and fig. 3 d the hollow base of the same 

 incompletely formed tooth seen from below. 



Besides the fossil jaws, teeth, and vertebrae of the extinct Gavial, a nearly entire 

 femur (fig. 9) of a Crocodilian has been discovered in the Eocene deposits at 

 Bracklesham, which in its proportions, agrees with that bone in the Gavial of the 

 Ganges. Cuvier, in his comparison of the bones of the Gavial with those of the 

 Alligators and true Crocodiles, merely observes, " La forme des os du Gavial ressemble 



