200 Transactions of the South African Philosophical Society. 



as a protection to the masseteric muscle. Behind this downward 

 expansion of the squamosal and somewhat internal to it there passes 

 outwards a prominent vertical ridge, between which and the part of 

 the squamosal which gives articulation to the quadrate there is left 

 a deep groove. This groove doubtless accommodated the external 

 auditory meatus. The whole structure of the squamosal, it will be 

 seen, presents a striking resemblance to that in the Polyprotodont 

 Marsupials (e.g., Thylacinus). 



The quadrate is not well preserved on either side of the skull- 

 Enough, however, remains to show that it was a fairly wxll-developed 

 element which articulated with the descending powers of the 

 squamosal. It appears to have had an ascending plate which rested 

 on the squamosal, somewhat after the manner of the quadrate in 

 the Anomodonts. 



The occiput is too imperfectly displayed to allow of description. 

 There is evidently, however, a median depression such as occurs in 

 Cynognathus. 



The lower jaw is well preserved on the right side of the skull. It 

 consists of a large dentary, large angular, and surangular, and a small 

 articular, with internally a small splenial. 



The dentary forms about two-thirds of the jaw. It is very much 

 more powerful than the dentary of Ictidosuchus, but not so powerful 

 as that in Lycosaurus, Cynodraco, or Cynosuchus. In front it 

 curves gently upwards, and does not form a " chin," as in Cyno- 

 suchus and most other known early Theriodonts. Posteriorly it 

 articulates with the angular and surangular. It has a large coronoid 

 process. 



Internal to the dentaries in front are a pair of slender 

 splenials. 



The angular is a shield-like bone lying between the dentary and 

 the articular. It rests on and almost completely hides from view 

 the surangular. A little behind its centre the bone is pierced by a 

 moderate-sized foramen. A round opening through the jaw is also 

 formed in the line of the suture between the dentary and the 

 angular, which probably corresponds to the large oval opening 

 through the jaw of the Anomodont. 



The surangular is apparently a large bone but is almost hidden by 

 the angular. It forms the whole of the upper margin of the 

 posterior part of the jaw. 



The articular is not well preserved. It appears, however, to have 

 been comparatively small, and to have articulated with the angular 

 and surangular in front. 



