300 DAVIDSON BLACK 



through this foramen but as already noted this is not the case in 

 Oreodon which in this respect resembles modern pigs. 



The parieto-temporal foramen consists of an irregular vacuity 

 above the petrous bone. The canal affords drainage for the 

 lateral sinus and for other venous channels in this region as 

 described above. The condition obtaining in this region in 

 Oreodon resembles that in the modern Bovidae but differs from 

 Sus, in which the temporal canal is not developed. 



The internal auditory meatus is placed below and slightly in 

 front of the well marked subarcuate fossa of the petrous bone. 

 At the bottom of the short wide canal the crista acustica marks 

 off the antero-superior opening of the facial canal from the pos- 

 tero-inferior acoustic area as in modern ungulates. 



The posterior lacerated foramen forms a slit-like irregular 

 opening at the side of the basioccipital. In its rostral part it 

 affords passage to the common carotid artery as already noted 

 and is separated from the foramen ovale by a stout bar of bone. 



The precondylar foramina are single and open forwards and 

 outwards. In addition to transmitting the hypoglossal nerves 

 these foramina apparently were also traversed by veins. 



Rhinencephalon^ 



The olfactory bulbs in Oreodon are large (figs. 23 and 24) and 

 are set obliquely upon the rostral extremity- of the massive 

 olfactory tracts. From the appearance of the casts of the cavi- 

 ties in which the bulbs were lodged, the impression is gained 

 that the lamina cribrosa extended well back over the dorsal 

 surface of the bulbs, which in their shape and relative size closely 

 resemble those of Orycteropus (vide Elliot Smith, 8 and 13). 

 The details of the configuration of the ventral and lateral aspects 

 of the bulbus are unknown but it is safe to conclude that the 

 area for attachment of the primary olfactory fibers extended 

 widely over these surfaces. 



As in Orycteropus, the large olfactory peduncles are visible in 

 a dorsal view of the brain. Ventrally they give rise to the medial 



^ The term Rhinencephalon is here employed in the sense defined by Elliot 

 Smith (9) in contradistinction to the Neopallium. 



