80 W. BLAXLAND BENUAM. 



direction of this furrow does not seem to agree with the view 

 that it is au isolated portion of the s. frontalis primus. 



Beyond the anterior end of the " sulcus frontalis primus " is a 

 rather short furrow, lying nearer to the median fissure, to which 

 it is parallel. It does not appear to be a separate portion of the 

 frontalis primus, for such portions are usually oblique, and the 

 upper lateral end is placed below, laterad of, the end of the 

 upper part of the frontalis primus. It appears to be possible 

 that it represents the "sulcus frontalis mesialis,'^ which 

 has hitherto been regarded as peculiar to man, and has not 

 been recorded for any anthropoid brain, and I do not wish to 

 insist upon this interpretation. The fissures in the oraug are 

 so variable that it is quite possible that this one is merely a 

 portion of the s. frontalis primus. 



The s. frontalis medius and s. frontalis secundus are com- 

 paratively short but distinct furrows having a longitudinal 

 direction. Both are independent of the vertical fissures. 



Them's, fronto-orbitalis," which in Cunningham's figure is 

 so conspicuous, is in both our orangs almost limited to the 

 orbital surface, only a small part coming on to the outer 

 surface. This portion presents the peculiarity that it appears 

 to pass into the sulcus prsecentralis inferior, from which, 

 however, it is in reality separated by a deep gyrus. 



Parietal and Occipital Lobes. — With regard to the 

 *' Affenspalte " our two orangs illustrate two different condi- 

 tions. In the small brain (No. 1) there is on each side a well- 

 developed operculum, and the intra-parietal passes into the 

 AflFenspalte below it. But in Rolleston's specimen, as he 

 described, the operculum is less developed ; the " arcus occi- 

 pitalis,'' or annectant gyrus, comes to the surface, so that the 

 parieto- occipital fissure is cut off from the Simian fissure. 



The arrangement of the ^' intra-parietal system " is exhibited 

 in the diagrams ; the right hemisphere of the one brain 

 resembles the left hemisphere of the other, and vice versa. 

 There is nothing special to be noticed about them, llolleston 

 fully described the specimen thirty-three years ago. 



