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SOME CARNIVOROUS THERAPSIDS. 103 
shortness of the temporal fosse, which are only about half as long 
as the width of the parietal bone. 
In Scymnognathus the parietal region is much narrower, and 
the temporal fossz nearly as long as the parietal region between 
them is wide. 
In Arctognathus the temporal fosse are longer than the parietal 
region 1s wide, and in the Cynognathids they are very long, and 
the parietals form a narrow crest. 
Brain-cavity of Scymnognathus. 
The specimen of ‘ Seymnognathus” shows the brain-cavity, 
although, owing to the hardness of the matrix with which it was 
filled, this is not very well preserved. Its main features are, 
however, quite certain, but it does not merita lengthy description. 
The general structure will be best understood from text-fig. 5. 
Text-figure 5. 
The brain-cavity of Scymnognathus whaitsi ? in sagittal section. X 1. 
There is a distinct resemblance to Diademodon owing to the 
comparatively thin basioccipital and the large opening to the 
vestibule through the posterior end of which the tenth nerve had 
its exit. The general features of the vestibule recall Diademodon, 
but there is no visible trace of a cochlea. 
The chief differences from the more recent animal are that the 
whole cavity for the cerebellum is very much smaller, and that 
its bage rises very rapidly in front, very much as it does in 
Dimetrodon. 
The prootic, although it extends further forward than in the 
Anomodonts and Dimetrodon, has more of the greater anterior 
