NERVOUS SYSTEM. VERTEBRATA. 387 



becomes the " parieto-occipital " sulcus. It is quite inde- 

 pendent of the calcarine, but parallel to its forked caudal 

 branches. In this brain the parieto-occipital appears to 

 join the intraparietal sulcus, but in reality the two sulci are 

 separated by a submerged gyrus (fig. 226). 



The intercalary sulcus is here independent of all other 

 sulci, and it is significant that its posterior extremity is 

 turned upward. This tendency becomes much more pro- 

 nounced in the higher Anthropoidea. 



In the situation corresponding to that in which the cal- 

 carine-intercalary union takes place in the Oarnivora and 

 Ungulata there is a small triradiate sulcus (x), which in 

 Human Anatomy is still often called by Broca's name 

 " postlimbic," in spite of the fact that the hypothesis of a 

 limbic lobe, which is implied in this name, is not now 

 seriously entertained. We might more aptly call it the 

 " compensatory " sulcus, in reference to its obvious role. 

 It will be seen to be a very constant element throughout 

 the Anthropoidea. 



There is a small transverse occipital sulcus on the left 

 hemisphere. And far forward on the apex of the hemisphere 

 there is a short sagittally-directed sulcus, which may repre- 

 sent an early phase of the sulcus rectus. 



The posterior rhinal fissure occupies a position on the 

 ventral and not on the strictly lateral aspect of the hemi- 

 sphere, whereas in the Lemurs the rhinal fissure occupies 

 the lateral aspect of the cerebral hemisphere. (Cf. also 

 with regard to this point, the cerebral hemisphere in Nycti- 

 pithecus trlvirgatus or Aotus felinus.) 



If the lips of the Sylvian fissure be separated, a small 

 insula is exposed, chiefly under the larger fronto-parietal 

 operculum. Its surface is smooth. 0. C. 1337 D a. 



D. 555. A cast of the cranial cavity of the Common Squirrel- 

 Monkey (Chrysothrix sciurea). 



D. 556. The brain of a Black-fronted Squirrel-Monkey ( Callithrix 

 nigrifrons), ( <?). The left hemisphere has been separated 



(figs. 227 & 228). 



2c2 



