54 W. BLAXLAND BENHAM. 



portions of the parieto-occipital are connected by a short but 

 deep sulcus. 



The vertical portion of the fissure, after thus joining the 

 superior portion, forks dorsally as shown (at b. and c.) ; below 

 the fork it passes straight downwards on the mesial surface, 

 and is continued on to the tentorial surface of the hemisphere, 

 where it joins the calcarine fissure — the gyrus cunei being quite 

 deep. We thus have the -<-shaped arrangement of this 

 system of fissures which Cunningham regards as typical for 

 man, but which he denies to the apes. 



On the right hemisphere (figs. 2 and 11) the lateral part of 

 the parieto-occipital is entirely separated from the mesial 

 vertical portion, and is completely surrounded by gyri (see fig. 

 15) ; its mediad end dips for only a very little distance down- 

 wards in the mesial face, and the vertical portion — the main 

 part of the fissure {mes. p. o.) — comes up to the upper surface of 

 the hemisphere in front of the fissure in question. So entirely 

 cut oflP is the upper part of the parieto-occipital that I at first 

 took it for a part of the Afi'enspalte, but its depth and other 

 relations, especially when compared with the arrangement on 

 the left side, show it to be a portion of the parieto-occipital, as 

 Beddard describes it. He, however, overlooked the gyrus 

 which cuts it off from the vertical part of the fissure, which also 

 he did not recognise. 



The separation of the parieto-occipital fissure into two dis- 

 tinct portions appears to be a rare occurrence. I do not find it 

 mentioned in descriptions of chimpanzees^ brains, and only rarely 

 is it recorded for man. Cunningham does not say very much 

 about it. He figures the ''normal" arrangement on p. 43, where 

 the fissure, at a point some distance below its upper end, gives 

 off two branches, one anterior and one posterior, to the main 

 track, which is separated from the calcarine fissure by a super- 

 ficial gyrus cunei ; but he represents no gyrus intercuneatus. 



What has happened in ''Sally"? The hinder of the two 

 branches of the parieto-occipital appears to have been cut off — 

 partially on the left, entirely on the right — from the rest of the 

 fissure. Cunningham represents several varieties in the arrange- 



