202 Annals of the South African Museum. 



3. the groove for the external auditory meatus does not 



continue on to the top of the skull ; 



4. the squamosal has apparently but one deep groove for the 



reception of the quadrate ; 



5. the molars are only cusped in a simple manner ; and 



6. in the anterior portion of the basisphenoid just medial to 



the end of the large groove between the bone and the 

 posterior ramus of the pterygoid there is on each side of 

 the bone a small foramen which may be a Vidian foramen. 

 This has been noted by Watson in a single Gorgonopsian 

 skull, but is not present in Diademodon. 



In all these features Diademodon can be considered a direct 

 advance upon Cynosuchus. The brain-structure of the two closely 

 approximates ; the nature of the dentition is not so close. The 

 latter is probably a secondary advance, although there is not very 

 much difference between the molars in Cynosuchus and in 

 Nythosaurus. 



Type. Somewhat crushed skull (S.A. Mus. Cat. No. 4333). 



Locality. Weltevreden, GraafT-Keinet, C.P. 



Horizon. Lower Beaufort Beds Cistecephalus zone (near top of). 



NOTES UPON THE BRAIN-CASE IN CERTAIN THERAPSIDA. 



DINOCEPHALIA. -Hitherto comparatively little has been known 

 about the detailed structure of the brain-case of the Dinocephalia. 

 Watson, in his paper on the Order, has given the fullest account 

 of the region and, inter alia, says : <: There is a relatively small 

 brain-cavity. This is throughout higher than wide and has not 

 -been cleaned in any specimens ; fractures, however, show that it 

 possessed the characteristic Therapsid character of having the 

 large opening to the vestibule placed very low down in the skull. 

 The floor of the brain-cavity rises considerably towards the front." 

 Fortunately it has been found possible to obtain a sagittal section 

 of the back part of a large Tapinocephaloid skull from the Gouph 

 in the collection of the South African Museum, and to trace 

 the position of the foramina opening into the brain-cavity. It 

 has not been possible to work out, however, the structure of the 

 inner ear on account of the intractability of the matrix. The follow- 

 ing account contains incorporated in it the account published by 

 Watson. 



