352 



PEOF. G. ELLIOT SMITH ON THE 



immediately external to this : it is interposed between the adjacent ends of the lateral 

 and coronal sulci. In Milne-Edwards's specimen of this species the correspondmg sulcus 

 is represented as being fused to the coronal sulcus (Hist. Madag. (2) tome vi. pi. 86. 

 fig. 2), just as the coronal sulcus is united to the furrow e in Lrmnr, and also in 

 ray specimens of Prop it heats Eihoardsi (figs. 28 and 29), F. Verreanxii (fig. 26), and 

 P. CoqvereU (fig. 27). On the right hemisphere of P. dladcma (figs. 22 and 24) the upper 

 sulcus (/) is longer, and the upper end of the lower transverse sulcus {e) is bent back 

 behind the end of the lateral. 



Fig. 26. 



SCO. 



Fig. 2G. — Fnipitheciis Verrcaimi. Plan of the sulci on the flutcrior portion of another left 



eerebrul hemisphere. Nat. size. 

 Fig. 27. — Pi-opitlients Cwiucrdi. Plan of the sulci on the anterior portion of the right 



cerebral hemisphere. 

 Fig. 2S.- — Propithecus Edwardsi. Ditto. 

 Fig. '29. — Ditto. I,eft hemisphere. 



In the specimen of Fropithecus Udwardsi (figs. 28 and 29) the arrangement found iu 

 Lemur is reproduced. The small furrow f is oblique, as it is in Lemur. On the left 

 hemisphere the upturned caudal apjieudage {e) of the coronal sulcus is apparently 

 separated from the main coronal element. 



In Propithecus Coquereli there is no furrow f, and the sulcus e is unusually Jong 

 (fig. 27). It is joined to the coronal at a right angle, and overlaps the end of the lateral 

 on the caudal side. An exactly similar state of alfairs is found in one specimen of 

 Propithecus Verreaitxii (flg. 26) ; but in another specimen (fig. 25) of the same species 

 there is a long typical central sulcus, like that found in Perodicticus : it clearly 

 represents a fusion of elements c and /' and their complete emancipation from the 

 influence of the coronal and lateral sulci. 



The arrangement of the bony ridges corresponding to the cerebral sulci in a cranivxm 



