1052 



DR. R. BROOM ON THE ORIGIN 



[Dec. 10,. 



very imperfectly known in the Cotylosanrians, and even in the 

 Pelycosaurs there are one or two points in doubt, and in Gale- 

 chirtis both the palate and temporal region are unknown. 



Text-fig. 244. 



S^ny. 



Dent. 



^T-t 



E ^ 



Mandibles of Mammal-like Reptiles. 



A. Froeoloplion triffoniceps. 



B. Galechirus scholtzi. 



C. Dicynodon jouherti. 



D. Lycosuclnis vanderrieti. 



E. Cynognathus platyceps. 



F. Gompliognatlms kannemeyer-i 



^M^., angulare; ^rt., articulare ; Co., coronoid ; Dei j^., dent ary ; 

 S.Anc/., sur-angulare ; Sp., splenial. 



The mandible is, however, well known in most types. In 

 Procolophon the anterior half of the jaw is formed of two boxes, 

 the dentary forming the outside and supporting the teeth and a 

 large splenial, which forms the greater part of the inside. 

 Immediately behind the row of teeth is a well- developed little 

 coronoid bone. On the inner side, at the back of this bone and 

 near the top of the jaw, is a large oval opening into the large 

 cavity of the posterior part of the mandibles. On the outer side 

 of the jaw just behind the dentary is seen the large angular and 

 surangular, each forming about half of the outer surface of the 

 posterior half of the jaw. The angular appears to pass back 

 to the angle of the jaw and to form the whole of the inner side of 

 the posterior part, the surangular forming the upper border.. 

 The articular is small and wedged in between these two bones. 

 In Pareiasaurus there is certainly a large angular and a large 

 splenial a little like that in Procolophon, but the posterior part of 



