306 DAVIDSON BLACK 



of the neopallium in Oreodon, the transverse diameter of whose 

 cerebrum practically equalled that of Sus. 



3) The general somatic sensory projection area possibly lay 

 lateral to the corono-ansate sulcus and extended caudally as far 

 as the processus acuminis ectosylvii (v. Campbell, 1. c). 



4) The motor projection area probably occupied the cortex 

 medial and to a small extent lateral to the corono-ansate sulcus 

 and extended rostrad to the presylvian sulcus (v. Simpson and 

 King, 29; Campbell, 1. c; Broclmann, 1. c). 



Association fields in connection with these last two projec- 

 tion areas would seem to have been but slightly developed, as 

 evidenced by the relatively very small dimensions of the rostral 

 portion of the casts. The prominence of the two gyri bordering 

 the coronal sulcus implies, however, a considerable local func- 

 tional activity such as might be expected in the somatic sensory- 

 motor projection area of an animal equipped with such a highly 

 organized cerebellum (vide infra). 



Cerebellum 



The dorsal surface of the cerebellum in Oreodon was fully 

 exposed and even a small area of the midbrain must have been 

 visible from above, owing to the slight caudal development of the 

 occipital portion of the neopallium. Among modern forms the 

 nearest approach to such a primitive cerebral condition is to 

 be seen among the Edentates, though in all of the latter forms 

 the occipital neopallial expansion is more extensive than in Oreo- 

 don. In contrast to this primitive condition of neopallial devel- 

 opment, the cerebellum in Oreodon, in the arrangement and 

 development of its parts, shows a plan of organization very simi- 

 lar and in no way inferior to that obtaining in modern artiodac- 

 tyls, while its bulk compares quite favorably with the volume of 

 this organ in Sus (vide supra, p. 296). 



Lobus anterior and lobulus simplex. Although but little doubt 

 can remain as to the homology with the fissura prima of the well 

 marked transverse depression visible on the dorsum of these 

 casts (vide figures 9 and 10). the anterior lobe and lobulus sim- 

 plex will be considered together since it is the combined fea- 



