210 Annals of the South African Museum. 



, 



in front of the meeting place of the two bones the parietal lies 

 above a plate of bone which forms the upper border of the hypo- 

 physial fossa and passes down some distance on its front border 

 to meet the basisphenoid. Anteriorly this bone which occupies 

 the position of the parasphenoid of the Dinocephalia, at least in 

 its lower half meets the pterygoids. 



The vertical ascending plates of the pterygoids are separated 

 from one another in two places. The first is seen in cross-section 

 just above the palatal surface at the level of the lateral flanges. 

 The other separation is the passage for the olfactory portion of 

 the brain which passes upwards and forwards through the opening, 

 doubtless swelling out anteriorly to form the olfactory lobes. 



Scylacops capensis. A skull of this species (Cat. No. 3444) from 

 Well wood, Graaff-Reinet, C.P., which was fractured longitudinally, 

 has the bone so brecciated that the structure of the brain-case is 

 indeterminable. It can be seen, however, that the posterior portion 

 is somewhat longer and not so high as in the larger forms and the 

 transverse pro-otic plate is not so vertical. The stapes is seen 

 lying in position between the fenestra ovalis and the quadrate. 

 The bone at its outer end, is not rod-like, as it frequently seems 

 to be when the under surface only is cleaned, but plate-like with a 

 slightly convex anterior face and a parallel concave posterior face. 

 The upper surface is expanded with a flat horizontal posterior 

 projecting plate. 



THEROCEPHALIA. Alopecognathus minor. Although the matrix 

 of the type of this species which is from the upper part of the 

 Tapinocepkalus zone is too resistant to allow of much develop- 

 ment, the region of the brain-case has been broken through in 

 several directions so that a certain amount of its structure has 

 been made out. 



In front of the foramen magnum the brain-case swells out laterally 

 and vertically. The basioccipital forms most of the condyle. On 

 the ventral surface of the skull it forms the anterior border of 

 the fenestra ovalis and articulates with the basisphenoid in a 

 jagged suture lying between the fenestrae ovales. In sagittal 

 section, however, the basisphenoid is seen as a thin plate underlying 

 the basioccipital which extends forwards above it to well in front 

 of the level of the internal auditory meatus. 



