296 



THE INTERMEDIATE PRIMATES 



cruciate fissure in lower mammals. It has a slight obliquity lorward, however, 

 approximating the general angulation of this fissure with the superior longi- 

 tudinal fissiire as seen in the higher anthropoids and man. The frontal lobe 



DORSAL SURFACE OF BRAIN, PAPIO CVNOCEPHALUS. 



[Actual Length 77 mm.] 



Key to Diagram, sulc. p. inf., Sulcus Precentralis Inferior; sulcus retrocentralis inf., Sulcus Rctro- 



centralis Inferior; sulcus temporalis sup.. Sulcus Temporalis Superior. 



Stands out sharply because of its marked orbital concavity into which the 

 orbital plate of the frontal bone projects. A well-defined hssure of Sylvius 

 extends backward and upward, more oblique m its general direction than 

 that seen in the lower primates. It demarcates a well-defined temporal lobe 

 the tip of which projects forward for a considerable distance, giving it partic- 

 ular prominence in front of the horizontal limb of the fissure of Sylvius. A 

 well-marked and long sulcus simiarum separates the parietal from the occip- 

 ital lobe, thus completing the topographical outline of the major hemi- 

 spheral lobes on the convexity of the brain. The convolutions and fissures 

 are richest and most complex in the parietal and temporal lobes, and least 

 pronounced in the frontal lobe. The entire surface configuration and the 

 arrangement of the fissures produce the impression of a gyrencephalic pat- 



