ENDOCRANIAL ANATOMY OF OREODON 307 



tures of these parts that reveal their essentiaUy rummant 

 characteristics. 



The area in question is clearly marked out on all the casts as 

 that part of the cerebellum which lies directly rostrad of the 

 prominent postero-median lobule and whose division into medial 

 and lateral moieties is not sharply indicated by grooves. The 

 folia in the mid-dorsal region of this area have expanded to form 

 a characteristic elongated median prominence which merges 

 gradually into the depressed, laterally situated portions. In other 

 words, the chief growth expansion of the folia in this region has 

 been in the sagittal direction and has been greatest in the mid- 

 sagittal plane (v. Bolk, 1. c). As a consequence, the rostro- 

 caudal extent of the area in question when measured in the 

 mid-sagittal plane is practically equal to that of the caudally 

 situated cerebellar parts. 



Laterally the depressed portions of this region are encroached 

 upon by the forward growth of the ansiform lobules and so become 

 much reduced in rostro-caudal extent. In spite of this, the part 

 in question is in contact laterally with the crus ascendens of the 

 formatio vermicularis for a considerable distance, being separated 

 therefrom by the rostral part of the fissura parafloccularis. 



In all the above features the cerebellum of Oreodon shows 

 marked resemblance to that of ruminants (e. g., Ovis, Bos, Cer- 

 vus) and presents an equally marked contrast to that of Sus. 



Lobulus mediamis posterior. In Oreodon this division of the 

 posterior lobe is strongly developed and is folded upon itself to 

 form a sigmoid-shaped lobule which protrudes high above the 

 level of the adjacent anso-paramedian area. A similar develop- 

 ment of this lobule is characteristic of most modern ungulates, 

 the few exceptions being chiefly among the smaller members of 

 the group (e. g., Hydropotes). 



Lobulus ansiformis. This lobule is relatively well developed 

 in Oreodon and its folia are apparently arranged in the form of 

 two crura, separated by a short intercrural sulcus. Among mod- 

 dern ungulates a loop-like ansiform lobule is characteristically 

 developed in Sus in which the lobule is essential similar to the 

 corresponding region in carnivores. In Bos and Equus a some- 



