48 



MR. D. M. S. WATSON ON THE 



is earned by a spout-like projection from the pro-otic, its inner 

 border is basisphenoid. Tliat bone immediately in advance of 

 the foramen has a deep depressed groove. There can be no 

 doubt that this foramen is for the fifth nerve, the cavity before 

 it having housed the Gasserian ganglion. Above and in front of 

 this foramen the pro-otic is continued forward, having a suture 

 with the basisphenoid, until its anterior margin or that of the in- 

 distinguishably fused supraoccipital is cat into by a notch, which 

 is very nearly converted into a foramen by the basisphenoid. 

 This foramen must be venous; it is in part the homologue of one 

 which is almost constantly represented in Therapsids. 



The supraoccipital is as always spread out into a wide plate, 

 but from the anterior part of this expansion a special thickening 



Text- figure 9. 



Par. I.R 



QuJ. Qu. Pr.At. B.Oc. B.Sp. 



Sci/innocjnatJius wliaitsi Broom. R. 4053. B.M.N.H. 



Occipital aspect of skull, witli the antei-ior ends of the proatlas attached. X-g. 



Pae., parietal ; Qu., quadrate; T.B.Sp., tuber hasi-sphenoidalis. 



is carried forward, forming the roof and part of the side-wall of 

 the bi-ain-case. It is this thickening whose margin forms the 

 dorsal border of the venous notch. With the sides of the upper 

 part of the supraoccipital in the region of this thickening the 

 interparietal articulates, stretching far forward in contact with 

 the parietal above and the supraoccipital below, and widely 

 exposed in the outside view of the brain-case. 



The basisphenoid is a remarkable bone, which in the speci- 

 men is broken ofi" in front. As far as it is preserved, how- 

 ever, it consists of a body which is articulated with the front of 

 the basioccipital largely through the intermediary of the two 



