52 MR. D. M. S. WATSOxX ON THE 



bottom of tlie skull. There is a single bypoglossal foramen in 

 the usual position. 



Taken as a whole, it is obvious that the brain-cavity was very 

 small in relation to the skull, and especially that the cerebral 

 hemisphei'es were still of much less bulk than the cerebellum. 

 At the same time the very great proportional length of that part 

 of the brain which lies in front of the fifth nerve foreshadows 

 the great cerebral development which occurred in later allied 

 forms. 



The palate of Scymnognathus tvhaitsi is still not known as a 

 whole, but the anterior part is very well shown in the sections 

 of 49369, from a reconstruction made from which text-fig. 10 is 

 mainly drawn, and in the solid in R. 4052. The pterygoidal flange 

 and one transverse bone are preserved in position in E,. 4053, and 

 that individual i-etains a small fragment from the middle of the 

 palate just in front of the anterior end of the long pterygo- 

 parasphenoid bar. This fragment shows a pair of much raised 

 ridges, which lie on the pterygoids and diverge outwards as they 

 ai-e traced forward. These are covered with a shagreen of small 

 teeth. Between these the palate is deeply grooved ; lateral to 

 them it is depressed into deep hollows. The dorsal surface 

 of the fragment bears a deep median keel. This fragment has 

 been cut across by a tranverse cut, so that it now shows three 

 sections. That at the back shows that the keel is formed by a 

 single bone whose lower edge is received into a groove on the 

 upper surface of the fused pterygoids, which meet below it. 

 In the middle section this median bone has a deeply gi'ooved 

 lower edge, the two thin ridges which form the side-walls of this 

 groove being received in slits in the pterygoids. These latter 

 bones meet in a median suture on the palate and here bear the 

 massive tooth-bearing ridges. On the front section the median 

 bone is exposed on the palate, forming the roof of the median 

 groove and separating the pterygoids. The median bone thus 

 corresponds exactly in position and relations with the posterior 

 median bone in Gorgonops and the back of the vomer in Diade- 

 modon. The anterior part of the palate resembles that of Gor- 

 gonoi^s in the relation of the internarial bar to the palatine 

 process of the pi-emaxilloe and in its shape. 



Near its anterior end the internarial bar is a single bone 

 with a convex dorsal surface from which a ridge rises. This ridge, 

 which is detached, apparently by fracture, extends upwards and 

 biickwards, obviously repi'esenting an ossification in the nasal 

 septum. The lower surface has a low median ridge separating 

 two well-defined gi-ooves. As this bone is traced backward it 

 gradually becomes narrower from side to side until in the region 

 of the first molar tooth, where it is seen in section (text-fig. 12), it 

 has become convei'ted into a plate 35 mm. in depth and only two 

 millimetres thick at the lower edge, where it is widest. The 

 dorsal centimetre of this narrow septum is clasped between two 



