ON THE UAKARI MONKEYS. 

 Fig. 9. 



121 



P. Z. 8. 1880, 

 p. 643. 



The same, left half, seen from the outside. 

 Fig. 10. 



The same, from the inside ; the cerebellum and medulla have been removed. 

 All the figures of the natural size. 



s. Sylyian fissure ; p.p. Postero-parietal ; s.f. Supero-frontal ; s.a. Supra-angular ; 

 a.t. Antero-temporal ; t.o. Temporo-occipital ; c.m. Calloso-marginal ; c. Calca- 

 rine ; cl. Collateral ; o.p. Occipito-parietal. 



developed angular gyrus. The union of the temporo-occipital and ' g^ 

 occipito-parietal (the two parts of the scissure occipitale of Broca) sulci 

 divides off perfectly the occipital and parietal lobes ; so that there is here 

 no such superficial " pli de passage " between these two lobes as exists 

 in Cebus capucinus and Pithecia satanas. In P. monachus there is, in 

 addition, a second, more superior passage-fold between these two lobes 

 (Flower, I. c.)*. In Cebus apella (according to Gratiolet's figure, 

 I. c. pi. 10. figs. 12, 12 bis\ as in Brachyurus, the "pli de passage " is 

 concealed, so that superficially the two lobes appear perfectly distinct. 



Anterior to the supraangular sulcus, the fissure of Rolando (p.p.) 

 (postero-parietal, Huxley) is seen as a well-developed sulcus forming a 



* As regards this and sundry other differences between Pithecia monachus and 

 P. satanas, it must be remembered that the two are not perhaps strictly congeneric, 

 P. satanas having been separated, with P. ckiropotes, as a genus Chiropotes. 



