208 Annals of the South African Museum. 



The foramen for the exit of the Vlth nerve is seen considerably 

 in advance of the vestibule, more than half-way up the sloping 

 portion of the floor. It is a small foramen, but the course of the 

 passage of the nerve has not been determined. 



The notch at the top of the sloping portion of the floor is saddle- 

 shaped. On either side of it the bone is prolonged forwards by 

 two short processes the processi anteriores inferiores of the 

 prootics. 



The side-wall of the posterior part of the brain-case is nearly 

 vertical seen from within. Just above the vestibule it is somewhat 

 excavate possibly the depression is the fossa sub-arcuata. On 

 the wall are two large oval foramina separated by a thin splint 

 of bone. The anterior of these lies just behind the anterior wing 

 of the sloping floor, and with its longer axis inclined. The side- 

 wall of the case is here very thin, and the canal from the foramen 

 is short, passing outwards and downwards. This foramen is 

 probably the incisura prooticum for the exit of branches 2 and 3 

 of nerve V. Slightly posterior to and above the foramen is a 

 more irregularly-shaped opening, which is probably the equivalent 

 of the venous foramen figured by Watson in Diademodon. 



The basioccipital and basisphenoid are separated by an ill- 

 defined suture occupying the position seen in a well-preserved 

 skull of Scylacops capensis. The suture runs from the middle 

 of the lower border of the fenestra ovalis slightly forwards to the 

 median line of the deeply-vaulted region between the basisphenoid 

 keel and the basioccipital condyle, and then back to the fenestru 

 ovalis of the other side 



Posteriorly the under surface of the basisphenoid is deeply 

 vaulted ; the under surface suddenly bends vertically downwards 

 and becomes a median keel passing forward to meet the pterygoids, 

 between which the anterior portion seems to be clasped. The 

 lateral ventral ridges are thick, but are not swollen into tuberosities. 

 They form the anterior borders to the fenestrae ovales. Above 

 the fenestra ovalis the suture between the pro-otic and the basi- 

 sphenoid runs upwards and forwards to the lower posterior border 

 of the pituitary fossa. The lower and anterior borders of this 

 high, short opening are formed by the basisphenoid which continues 

 forward as a vertical median sphenoid clasped by the vertical 

 median plates of the pterygoids. Below the pituitary fossa and 

 posterior to the suture between the pterygoid and the basisphenoid 



