96 



It looks as if this area had thrust itself in below the bent portion of the 

 sulcus post-centralis of pithecus and thrust it up straight, at the same 

 time separating widely the sensory from the visual area — the latter 

 almost disappearing on to the mesial surface of the hemisphere. It 

 will be noted that the gyrus supramarginalis and the gyrus angularis 

 of man are quite unrepresented histologically in pithecus. 



Sul. par. sup. Sul. cinguli 



Sul. cinguli Sul. cent. 



— Arcus cinguli 



- - Sul. paracingali 

 Sul. postcent. 



Sul. par. sup. 

 Sul. par. horizon. 



Sul. par. inf. 



Sul. par. horizont 



Sul. cent. 



Arcus cinguli 



_ Sul. paracinguli 



- Sul. postcent. sup. 



Sul. postcent. inf. 



Fig. 2 A. 



Fig. 2 B. 



Sul. par. sup. Sul. cinguli Sul. cent. 



Arcus cing 



Sul, par. horizont 



Arcus par. occ. 



Fiss. par. occip. Sul. cinguli 



Sul. postcent. inf. 



Sul.paroccip. ^ , , . 



' Sul. par. honz. 



Sul. postcent. inf. - - 



- Arcus cinguli 



- Sul. centralis 



Sul. paracingul. 



Fig. 2 C. Fig. 2 D. 



Fig. 2. In A and B very simple combinations are displayed, but C is difficult 

 to account for, though it is an excellent example of areas cinguli. In A, also, a 

 very beautiful example of the arrangement of the parietal furrows it to be seen 

 (see Ref. (1). D is open to the same criticisms as 1. C. in the preceding illustration. 



The change in direction of the sulcus post-centralis is a great but 

 not extraordinary one. Other sulci are known to undergo equally 

 great alterations, e. g. the calcerine sulcus, which in some animals 

 is almost vertical, though in most others it is horizontal. Elliot 



