On a Neiv Rcvtilc (Proterosuchus fergusi). 163 



is very similar to that which probably occurred in the primitive 

 Ehynchocephalians. 



The lower jaw^ also more closely resembles the Ehynchocephalian 

 type than it does that of the other orders. The structure of the 

 lower jaw is only fully known in Procolophon among the early types, 

 but so far as preserved the mandible of Proterosuchus is essentially 

 similar to that in Procolophon. 



We may therefore conclude, on the present evidence, that Pro- 

 terosuchus is a primitive Ehynchocephalian which shows a consider- 

 able degree of specialisation along the line which gave rise to the 

 early Crocodiles and Dinosaurs. 



