()4-4 MR. \V. A. FORBES ON THE UAKARI MONKEYS. [NoV. 30, 



joined by the collateral sulcus^ (cl), which passes forwards and 

 slightly outwards, so appearing on the external face of the temporal 

 lobe (fig. 9). The temporal lobe has, in addition, a slight impres- 

 sion anterior and internal to this, but is otherwise quite smooth 

 below. 



The corpus callosum is well developed ; it is nearly ] inch in 

 total length ; the prsecallosal part of the cerebrum is 0'45 inch, 

 the postcallosal 0'9 inch in length. 



The cerebellum is well developed : the superior vermis is 085 inch 

 in length ; with the lateral lobes it is altogether r2.5inch trans- 

 versely. The flocculi are large, and the j)ons Varolii well developed. 

 The medulla has distinct olivary bodies. 



In the general characters of its brain, as will be thus seen, 

 Brachijurus approaches most nearly the genera Cebits and Pithecia 

 (including Chiropof.es), and especially tlie tyjjc found in Gebus apella. 

 "With Ateles and Layothrix it has no close relationship ; and the 

 same may be said as regards Mycetes ; it also departs widely in the 

 greater complication and development of the brain from Cadithri.r, 

 Chrysothrlx, and the smaller (^ebidaj genei'ally. 



Reviewing the facts already stated as to the structure of Bia- 

 chyurus 7'ubicundus, it is evident that Brachynrus is a perfectly 

 good genus, more or less intimately related to a number of the 

 larger Cebine forms, but nevertheless characterized by a combination 

 of characters peculiarly' its own. A rebitionship to Mycetes, sug- 

 gested by its external appearance and the form of the lower jaw, is 

 not borne out by its visceral anatomy, the brain and liver both pro- 

 nouncing decisively against the idea, besides other peculiarities. 

 With Ateles and Layot/irix it has no ])articular features in common, 

 but it undoubtedly approaches Celjus in the structure of its brain ; 

 and it is with this genus and Pithecia (including Ghiropotes) that it 

 has probably the nearest affinities. 



The institution of a genus OuaJcaria for the reception of these 

 short-tailed Monkeys by Dr. Gray (P. Z. S. 1»49, p. 9) seems to 

 me unnecessary. As he there remarks, the genus Biachyunts, as 

 originally proposed by Spix (Sim. et Vespert. Bras. p. 11), con- 

 tained two species, B. israelita (I. c. pi. vii.) and B. ouakary 

 (pi. viii.). 'J he former of these is now generally referred to the 

 genus Pithecia, standing as Pithecia chiropotes (cf. Sclater, P. Z. S. 

 18/1, p. 228). Having examined skulls of all the known species 

 of Brachyurus, as well as o{ Pithecia satanas, which is merely a repre- 



Prof. Flower says of Mycetes Q. c. p. 337), " the dentate sulcus is continuous 

 with the calcarine." On the other hand, in Ateles (cf. Huxley, ?. c. p. 2.55, 

 fig. 2) it is superficial and obvious. Broca also figures its existence in Zao'oi'Ar/.r 

 (/.c. p. 471, fig. 31). 



' This junction, at least superficially, of the calcarine and collateral sulci I 

 also find exists in_ Cehus cajmchuis (cf. also Gratiolet's figure. Atlas, pi. x. fig. 9) 

 and Pithecia safanus ; in Ateles and Kyct/jiit/ieciis, &e., however, it does not 

 exist, as far as I have seen, nor do I find any allusion to such a condition existing 

 at all in any of the memoirs ali-eady quoted on the braiu of Primates, 



