PAPIO CYNOCEPHALUS 



297 



tern of moderate simplicity, in w hicii, however, may be discerned all the 

 characters which hiter are more perfectly outlined in the higher 

 anthropoid hemispheres. 



FIG. I3(). BASE OF BRAIN, PAPIO CYNOCEPHALUS. 



[Actual Length 77 mm.] 



ORBITAL AND CEREBELLAR CONCAVITIES 



As already indicated, the orbital concavity is a prominent feature, as is 

 the case in all lower primates. Its inner margin is formed by a marked inter- 

 orbital keel, along which the olfactory tract and bulb extend, the tract being 

 readily detachable up to the olfactory trigone. The incipience of a gyrus 

 rectus may be discerned in the beginning of an olfactory sulcus. The angu- 

 lation of the chiasm with the tracts is typical of the primates. The cerebellar 

 concavity is especially deep and most pronounced in the median line caudal 

 to the splenium of the corpus callosum. 



THE ENDBRAIN AND OTHER STRUCTURES 



The basal surface of the endbrain, in its convolutional pattern, shows 

 a distinct but somewhat feeble design typical of this region in the Anthro- 



