442 



the "calcarine fissure" is merely the involution of the whole stria- 

 bearing cortex. 



If the lips of the fossa striata be drawn apart in the fresh brain 

 of almost any of the Apes, the condition represented in Figure 7 will 

 be exposed. The area striata is a broad, fiat, deeply depressed area, 

 whereas the gyrus fornicatus, which is partly submerged in the anterior 



s. call. marg. 



s. lim. praecunei 



foss. par. occ. 



s. i. ui. (r. d.) 



foss. str. occ. 



s. collat. s. lini. inf. ar. sti". 



s. lim. anterior areae striatae 



Fig. 7. The mesial aspect of the right occipital region of a Cercopithcciis aethiops, 

 in which the lips of the fossa striata and of the fossa parieto-occiiiitalis have been drawn 

 apart. The dotted lines represent the edges of the lips. s. lim. anterior areae striatae 

 =■ sulcus occipitalis, praestriatus = sulcus calcarinus proprius hominum. s. i. m. (r. d.) 

 = ramus dorsalis of the fossa striata =^ so-called "fissura calcarina". 



part of the fossa, is a prominent vertical column. Between these two 

 regions there is a slight vertical furrow, because the adjacent parts of 

 the area striata and the gyrus fornicatus are placed at right angles 

 the one to the other: in some cases, however, there is no distinct 

 angle between the two surfaces. If a horizontal section be made 

 through the fossa striata the vertical furrow (when present) will be 

 found to coincide exactly with the anterior edge of the stria Gennari; 

 to be, in fact, a sulcus limitans anterior areae striatae or, to use a 

 less ponderous name, a sulcus praestriatus. It is, however, hardly a 

 true sulcus, for at most it is a shallow open furrow. It is almost 



