ENDOCRANIAL ANATOMY OF OREODON 



291 



The fossa for the lodgement of the posterior clinoid processes 

 is shallow and the basioccipital surface between the posterior 

 lacerated foramina is considerably narrower than in the speci- 

 mens described above. The ridges corresponding to the internal 

 carotid arteries are not so well marked as in Specimen II. 



For.ov. /A-c.i. 



Tr b.Hub. 



'For. con. 



17 



Pa. ect. 



18 



Cerebral hemispheres. The convolutional pattern of the cere- 

 brum on both sides corresponds quite closely to that obtaining 

 in Specimen III. However, an additional compensatory sulcus 

 behind the ramus descendens suprasylvii is present on the left 

 side in Specimen IV instead of on the right as in the preceding 

 specimen. On both sides a small notch is present on the supra- 

 sylvian sulcus just rostrad of the level of the processus acuminis 

 ectosylvii as in Specimen I. 



