PARIETAL REGION IN THE PRIMATE BRAIN 325 



terior limit is the second, inconstant, branch of the interparietal 

 mentioned above lying between areas 5 and 7. InHylobates this 

 tiny bit of sulcus is usually markedly lengthened . The original small 

 furrow which cut into the first annectant gyrus in front is more 

 constant and well defined and appears here also as a continuation 

 of the interparietal (proprius) in that just beyond it in the ante- 

 rior part of the ramus occipitahs there is an annectant gyrus or 

 the latter sulcus is distinctly shallower. 



The terminal portion of the interparietal, the ramus occipitahs, 

 Ues within area 19, it may turn upward underneath the opercu- 

 lum, forming the posterior limit of the first annectant gyrus, as 

 referred to above in Macacus. The same arrangement may oc- 

 cur in Hylobates or more commonly the main sulcus continues 

 downward and backward and the furrow behind the first annec- 

 tant gyrus joining the interparietal is new formed (Cunningham). 

 In both cases there is marked off the typical paroccipital sulcus, 

 while in the latter case, in which the ramus occipitahs seems to 

 bifurcate, we have the sulcus occipitalis transversus of Ecker, 

 which, since it is present with the lunate, cannot be derived from 

 it. It is the continuation of the ramus occipitalis, i.e., the lateral 

 branch of the transverse occipital, which forms the anterior hmit 

 of the peristriate area as we shall see later. 



In the lower apes the variable and inconstant foldings described 

 as superior postcentral probably cannot be looked upon as homol- 

 ogous with those which bear the same name in the Simiidae and 

 in man. They are in relation with different areas being located 

 farther forward in the lower types. A possible exception might 

 be made in certain cases of Semnopithecus which is closest to the 

 anthropoids, although it is readily conceivable than even in the 

 lower apes a true sulcus postcentralis superior might appear. The 

 fissure of this name in human anatomy is new formed and much 

 younger and is in relation in front with area 2 and behind the areas 

 5 and 7. In Hylobates it is still quite variable, equivalent at 

 times doubtless with the fissure of lower forms. It may be ab- 

 sent and even when well developed is usually separated from the 

 inferior sulcus by an annectant gyrus or is in addition shallower. 

 Within this area 7 above the interparietal, as a result of continued 



