

NERVOUS SYSTEM. VERTEBRATA. 417 



D. 609. The brain of a White-collared Mangabey (Cercocetnt* 

 collaris), ( $ ): the left hemisphere has been detached. 



There is no important difference from the foregoing or 

 from the Macacus-braius. The opercular fold in th> lower 

 margin of the occipital lobe of the right side is very 

 extensive, stretching forward into the temporal region ; it 

 is also deep, so much so that the collateral sulcus is repre- 

 sented by two short sinuous sulci only, there being 

 presumably no call for the greater amount of surface they 

 would provide if better developed. 



There is a slight tendency among these Cercocebut-hemi- 

 spheres to irregularity (more so than in Macacus) in the 

 arrangement of the collateral sulcus. 0. C. 1338 D c. 



D. 610. The brain of a Diana Guenon (Cercopithecus diana), ( $ ) : 

 the left hemisphere has been detached. 



The differences from Macacus (and also from Cercocebu*) 

 are insignificant, being attributable to the smaller size of 

 the brains in the present genus. The arcuate sulcus gives 

 no posterior branch in the right hemisphere and only a very 

 short one in the left. On the mesial aspect the collateral 

 sulcus is seen to be represented by three isolated sulci the 

 posterior of which appears to spring from the calcarine. 



0. C. 1338 E. 



D. 611. The brain of a Diana Guenon (Cercopithecus diana) : the 

 left hemisphere has been detached. The floccular lobes are 

 well preserved. There are three sulci in the collateral 

 group o the left hemisphere, two in the right hemisphere. 



O.C. 1338 Em. 



D. 612. The brain of a Lesser White-nosed Guenon (Cercopithecus 

 petaurista), ( $ ) : the left hemisphere has been detached. 



There is a slight irregularity in the collateral sulcus, 

 which in each hemisphere is represented by two sulci. 



O.C. 1338 B a. 



D. 613. The brain of a Lesser White-nosed Guenon ( Cercopithecut 

 pctaurista), ( cT ) : the left hemisphere has been detached. 



O.C. 1338 E a a. 



VOL. II. 2 E 



