the 5/:m// n/" Diademodon. ;il5 



iiiupr Cil^t; of the post- temporal fossa, wliu-li is reUitivcly 

 hiiji^cr tluiii in I hud-unodon, passes stiMJglit inwards, about 

 halfway to the foramen rnaf^nuiu and then turns vertieally : 

 it rises well above the foramen uuignuui and is then lost. 

 This suture separates the parietal from the cxoccipitalj 

 supraoecipital, and interparietal, 



Tlie paroeeipital proecsses are powerful and their anterior 

 faees are weathered away so as to show the striieture. 

 Slight differences in this structure and on the left side an 

 apparent suture suggest that each process is composed of 

 two parts, an upper and smaller, which is probably the 

 exoceipital, aud a lower the opisthotic. 



The bone forming the upper part of the post-tcm|)()ral 

 fossa is the parietal, and the suture which separates it from 

 the pro-otic part of the pcriotic is jjlainly visible on botli 

 sides. 



Along the suture runs a dee[) groove, and a broken area 

 along the top of the pro-otic shows that this was formerly 

 covered by a lamina, just as in Diademodoii. In the suture 

 is a small foramen opening outwards aud backwards. The 

 broken aV^e on the pro-otic is continued outwards and 

 downwards so as to show that there was formerly a strong- 

 lamina covering the groove leading from the pterygo- 

 paroeeipital foramen to the post-temporal fossa. 



The pro-otic bears a comparatively small process for 

 articulation with the pterygoid. 



The deep pit lying just external to and in front of the 

 condyle is very large and -nell shown ; it has ajiparently 

 four foramina o[)ening into it : — 



1. A small foramen passing directly backwards just abo\e 

 the condyle, 



2. A large foramen opening into the very bottom of the 

 pit. 



3. A small foramen opening forward. 



4. A small foramen opening inwards. 



Immediately to the outside and slightly in front of the 

 pit IS the fenestra vestibuli, an oval hole about five milli- 

 metres across. Except on the side towards the pit the 

 fenestra is surrounded by a wide Hat area. 



Slightly in advance of the fenestra vestibuli lies the small 

 oval toramen for the facial nerve ; and from it a narrow 

 groove, presuuuibly a suture, passes upwards and forwards 

 to cut the upper surface of the basispheuoid above the 

 posterior rim of the pituitary fossa. This suture separates 

 the pro-otic region of the periotic from the basispheuoid. 

 On the front end of the specimen the posterior face of the 



