the Skull of Diademodon. 327 



the brain-case, being represented by the process which I 

 have described above in Diademodon. 



The evidence on which he seems to rely is that in Dicyno- 

 donts, Deinocephalians, and Dromasauria the side of the 

 brain-case is overlapped by processes of the squamosals and 

 postorbitals oi- postfrontals, which meet and exclude the 

 parietal from the temporal fossa. In Dicynodonts and 

 some Deinocephalians I have been able to see this arrange- 

 ment, but even in these cases there is still a squamoso- 

 postorbital arcade. It appears to me simpler to regard the 

 condition in Dicynodonts, &c., as secondarily arrived at from 

 one resembling that in Cynodonts. 



The occurrence in the type skull of Cynognathus cratero- 

 notus of a small infra-temporal fossa lying between the jugal 

 and the squamosal appears to be conclusive evidence that 

 the temporal fossa of Therapsids does not represent the 

 infra-temporal fossa of Diapsids. 



This small infra-temporal fossa in Cynognathus was 

 correctly interpreted by Seeley. 



Systematic Revision of the Gomphognathid Genera Diade- 

 modon, Gomphognathus, and Diastemodon. 



In 1894 Seeley founded the genus Diademodon for some 

 fragments of jaws from the Karroo which showed molar 

 teeth with wide flat crowns ornamented with cusps and 

 ridges. The type species is Diademodon tetragonus, founded 

 on a small piece of snout, and to the genus were referred 

 D. hrachyiiara^ the type specimens being isolated teeth ; 

 D. mastacus, foimded on a piece of maxilla with three 

 perfect teeth ; and D. brotvni, founded on the middle portion 

 of a skull with one perfect tooth. 



In 1895 Seeley founded another genus, Gomphognathus, 

 distinguished from Diademodon by the cheek-teeth being- 

 worn down flat. 



The type species, G. kannemeyeri, was fonnded on a 

 mandible showing the teeth, to which was attached the back 

 of a skull and some cervical vertebrae. To this gcuns Seeley 

 referred an excellent skull lacking the lower jaw, which is 

 the type of G. poJyphagus, and another excellent sknll with 

 the mandible closed on the palate, which he referred to the 

 same species. 



More recently Seeley described a new species, Diademodon 

 entomophonuSj the type being the middle portion of a skull 

 with some teeth. 



Finally, in October 1908, Seelev described a new subgenus 



22* 



