204 Annals of the, South African Museum. 



* 



wall and lying obliquely forwards in the hole. This divides the 

 posterior foramen for the IX-XI nerves from the anterior opening 

 into the vestibule. A short distance in front of this opening is a 

 small oval foramen for the passage of the facial nerve. Above 

 and slightly in advance of the vestibule there is a deep depression 

 in the side-wall of the brain-case which is probably a floccular 

 recess. Slightly behind that is a small foramen which may be 

 the opening of the canal for the ductus endolymphaticus situated 

 as figured by Watson in Diademodon. 



The pro-otic forms the side wall of the case in advance of the 

 vestibule. It is pierced above its anterior inferior process by 

 two large foramina which are widely open laterally. The two 

 are only separated by a thin flange of bone. The lower is for 

 a branch of the Vth nerve, the upper possibly venous. In de- 

 scribing Lamiasaurus, AVatson said : ' The prootic, of course, 

 contributes to the fenestra ovalis, above which it is perforated 

 by the aquaeductus fallopii for the Vllth nerve." 



The hypophysis is very deep and short, descending far below 

 the level of the occipital condyle. Watson has figured the pituitary 

 notch in external view in Lamiasaurus showing the ind-like 

 epipterygoid partially covering it. The posterior wall of the 

 pituitary fossa has a slight median ridge with a shallow pit on 

 either side in the upper half. Laterally it curves round to form 

 the posterior edge of the lateral opening, and has an anterior 

 process above. The fossa, however, is not separated from the 

 posterior part of the brain-case by any transverse wall. Above 

 it the roof of the brain-case is pierced by a large hole which com- 

 municates with the pineal foramen by a very long, circular, slightly 

 curved tube. 



The bones of the brain-case have been described by Watson. 

 In this form there is no deep vertical area below the basioccipital 

 condyle the structure approximates more to that of Lamiasaurus 

 than to that of Mormosaurus. The fenestra ovalis does not lie 

 very much below the level of the bottom of the condyle and sections 

 show the stapes to be firmly fixed in it. 



The paroccipital process is seen to be composed of a fairly thin 

 plate of bone forming the posterior occipital face and a massive 

 anterior portion which is probably the fused opisthotic and pro-otic. 

 The suture between the basisphenoid and prootic is not visible. 



The parasphenoid is a median plate of bone forming the front 

 wall of the pituitary fossa. From the upper part of its posterior 



