ENDOCRANIAL ANATOMY OF OREODON 



309 



the intratonsillar sulcus. The descendmg crus is shorter than 

 the ascending Umb and terminates at the level of the internal 

 acoustic meatus. 



At its caudal termination the folia of the crus descendens form 

 a short non-pedunculated projection which is lodged in the well 

 developed subarcuate fossa of the petrous bone. This projec- 

 tion therefore constitutes a homologue of the lobulus petrosus as 



Figs. 25 and 26. Camera lucida outline of the right lateral surface of plaster 

 casts of the cerebellar fossa in Ovis and in Sus respectively. The relations cf 

 the exposed portion of the formatio vermicularis is shown and the parts lodged 

 in excavations of the petrous bone are indicated by shading. For further 

 explanation see text. 



defined by Bolk in carnivores, but is not homologous with the 

 cerebellar parts lodged in the so-called ' floccular fossa ' of modern 

 ungulates. 



The truth of the above assertion becomes evident when the 

 endocranial relations of the cerebellum in this region are exam- 

 ined in Ovis and Sus (figs. 25 and 26). In Ovis the whole ter- 

 minal bent portion of the crus descendens is lodged in a wide 

 shallow fossa formed between the squamous and petrous portions 



