212 Annals of the South African Museum. 



It has not been possible to clean the inner ear, but the region 

 is somewhat fractured and some of the details can be seen. The 

 lower portion of the side-wall of the brain-case is perforated by 

 a large hole, partly divided by the process of the paroccipital 

 above-mentioned. Behind this wall of bone is the opening for 

 the IX-XI nerves. Anterior to it the opening leads laterally 

 into two elongate cavities separated from one another, as seen 

 in cross-section, by a swelling of bone partly composed of prootic 

 and partly of what seems to be an opisthotic part of the par- 

 occipital. Ventrally the opening passes down, doubtless, to the 

 fenestra ovalis. 



Superior to the internal auditory meatus the wall of the brain- 

 case is provided with a broad rounded ridge, above which is a 

 fairly deep fossa subarcuata, bounded anteriorly and superiorly 

 by the prootic. Just anterior to the lower border of the vestibule 

 opening is a small canal passing downwards and slightly outwards 

 the aquaeductus fallopii for the Vllth nerve. 



The upper part of the prootic is pierced laterally by one large 

 foramen and possibly by another. The larger anterior one is for 

 part of the Vth nerve ; the possible posterior one venous. In 

 front of the larger foramen the pro-otic is carried forward and 

 upward as a processus anterior prootici. This, on one side of 

 the skull, is pierced by the foramen for the Vlth nerve. Superiorly 

 the prootic articulates with the parietal. 



The prootic forms the posterior border of the pituitary fossa ; 

 but it shows a striking difference from the bone in the Gorgonopsia 

 in that it does not meet its neighbour in the middle line to form 

 a high ascending transverse plate. The portion of the bone pierced 

 by the Vlth nerve is merely a lateral anterior process ; between 

 it and its neighbour the bone is deeply notched as in Diademodon. 



In front of the pituitary fossa there is no vertical plate of the 

 basisphenoid such as is seen in the Gorgonopsia I have examined, 

 but the basisphenoid is continued forward as a shallow, thin, 

 slightly upwardly inclined splint of bone whose outer side is 

 broadly grooved. This median splint does not articulate with 

 the vertical plates of the pterygoids, which are separated from 

 each other to accommodate a median canal, 



A medium-sized Therocephalian skull from Wilgebosch (Lammer 

 Kraal), Prince Albert District, C.P., shows some additional features. 



