166 MR. D. M. S. WATSON ON TIIE 
The general plan of the structure is the same as in the larger 
and older South African Pariasaurians, but the more remarkable 
specializations of the latter types are absent; for example, the 
quadratojugal, though it does extend forwards below the jugal, 
does not reach the maxilla, and the lachrymal has a large expo- 
sure in the orbital margins. The quadrate is present in the 
specimen at the extreme hinder end of the part preserved. 
General Discussion of the Skull. 
Basis Cranii.—The occipital condyle is rather unusual in 
the great development of the pit for the anterior end of the 
notochord, which renders it on the whole concave; a similar 
condition occurs in Diadectes and Limnoscelis amongst early 
reptiles, and in a still more marked form amongst the primitive 
amphibia Loxomma, Pteroplax, etc. The condition is a primitive 
one. 
The basisphenoid, except for its very great mass, agrees in its 
structure with that of most Cotylosaurs, having very powerful 
tubera and distinct basipterygoid processes. 
The parasphenoid, which is as usual indistinguishably fused 
with the basisphenoid, is of great length and touches the ptery- 
goid in front as in Labidosaurus, Seymouria, and many other 
Cotylosaurians. 
Brain-case.—The more remarkable features of the posterior 
part of the brain-cavity depend very largely on the fact that 
Pariasaurus is a large and very massively built animal. The great 
development of the supraoccipital region and its powerful fusion 
with the roof of the skull, so different from the conditions in 
such types as Procolophon and Labidosaurus, are probably pro- 
duced in response to a mechanical necessity. The long, low, and 
wide form of the brain-cavity is a very remarkable feature which 
is not, so far as I know, paralleled by any other reptile. 
The determination of the nerve-exits presents no difficulty, 
and the only unusual feature, the entrance of the VIIIth nerve 
into the ear on the anterior wall of the bony canal which forms 
the foramen jugulare, is, I believe, very largely dependent on the 
enormous size of the latter. 
The ear, so far as can be seen, is of a very ordinary descrip- 
tion, lying well up in the side wall of the brain-case. 
It is apparently certain that the VIth nerve did not pierce the 
bas'sphenoid but must have issued through the prootic fissure. 
Sphenethmoid.—The sphenethmoid was the name given by 
W. K. Parker tothe small ring-shaped bone which surrounds the 
anterior part of the brain in the frog (Cuvier’s os en ceinture). 
In the frog it is a ring-shaped bone, ossified in the cartilage of 
the anterior part of the brain-case, and lying between the mem- 
brane-bones of the roof of the skull and those of the palate, 
particularly the parasphenoid, which it directly overlies. The 
whole bone in this animal lies in advance of the points of exit 
