440 



In the higher Cercopithecidae, such as the genera Papio and Sem- 

 nopithecus, and in the Siraiidae the operculum seems to be partly rolled 

 back, as it were, by the expansion of the rest of the neopallium. In 

 such cases it often happens that the stria Gennari does not reach quite 

 as far forward as the edge of the operculum but ceases several milli- 

 metres behind it. More often than not this happens also in the human 

 brain: but the edge of the area striata is always sufficiently near to 

 the sulcus lunatus to establish the identity of the latter. In a con- 

 siderable proportion of human brains the stria Gennari ceases exactly 

 in the caudal lip of the sulcus lunatus (Fig. 4) or in the free edge 



s.i. 1. 



area striata 



lateral and of the 

 stria Gennni-i 



s. lunat 



s. 1. m. 



mesial end of the 

 stria Gennari 



s. t«mp. inf. 



/ 



gyr. cuuei 



foss. par. occ. 



Fig. 4. A horizontal section through the ofcipital region of the right cerebral 

 hemisphere of an adult Egyptian to show the relationship of the stria Gennari to the 

 sulcus lunatus ("Affenspalte") and intrastriate sulci. .«. i. I. sulcus occipitalis intrastriatus 

 lateralis (occ. superior), h. i. m. sulcus occipitalis intrastriatus mesialis (reti-octücarinus). 



of the operculum when it is present: and the coincidence of the two 

 is as definite as it is in the Cebidae and such Cercopithecidae as Ma- 

 cacus and Cercopithecus. Such cases atford us quite conclusive and 

 irrefutable evidence of the correctness of the identification of the sulcus 

 lunatus. I have examined the distribution of the stria Gennari in re- 

 lation to the furrow which, from a mere study of the surface, seemed 



