THE DICTNODONTIA. 259 



b. The nasals are excluded from the external nasal aperture. The 

 head very loni:; the teeih subcqual. Eoth the first and the 

 fourth mandibular teeth bite into grooves in the margin of the 

 upper Jaw. The premaxillo maxillary suture acutely angulated 

 backwards. The mandibular sj'mpliysis extends to at least 

 the fourteenth tooth, and the splenials enter into it. The 

 cervical and tergal scutes form a continuous series. 

 3. Gavialido'.. 



lihynchosuchus. Gavtalis. 



B. With the presacral vertebrse amphieoelous (the anterior vertebrae 

 sometimes opisthocoelous (?) ); and the posterior nares bounded 

 by the pnlatines, the pterygoids not being united below. (AH 

 these Crocodiles are extinct and pre-cretaceous.) 



a. With the external nares terminal. 



4. 2'elmiiaurid(E. 



7'eleosavrus. Gmiiopholis. 



Slreptospondi/lus. Slatjonolcpis. Galesaurus (?). 



b. With the external nares on the upper part of the base of the 



snout near the orbits 



5. Hclodimtidce, 



Belodon. 



There is a large number of extinct Beptilia whicli re- 

 semble tbe Crocodilia in tbe cbaracters of their pre-sacral 

 vertebras, but differ from tbem, and resemble Lacertilia 

 Chelonia, or Birds, in other res^Dects. 



These are the Dicynodontia, the Ornithoscelida, and the 

 Pterosauriu . 



YII. The Dicynodontia. — Dicynodon and Oudenodon 

 are lacertiform animals, sometimes of large size, with 

 crocodilian vertebrae, four or five of which are a,nkylosed 

 together to form a strong sacrum. The skull is massive 

 and lacertilian in most of its characters ; but the jaws are 

 like those of the Chelonia, and were doubtless cased in a 

 horny beak. Nevertheless, mo'^t of the species possess two 

 great tusks, which grow from persistent pulps, lodged in 

 a deep alveolus of either maxilla. The limbs appear to 

 have been subequal and massive, with short and stout feet. 

 The scapula and covacoid are simple and expanded, and 

 there seems to have been no clavicle. The pelvis is very 

 strong, with widely expanded ilia, ischia, and pubes. The 

 two latter meet in a median ventral symphysis, and the 

 pubis and ischium of each side meet and obliterate the 



