ON THE UAKARI MONKEYS. 117 



British Museum Catalogue 7, 13, 6, 3, 18, for both B. calvus and B. 

 melanocephalus. In the latter skeleton (" OuaTcaria spixii" 806 6) I 

 counted, however, nineteen or twenty caudal vertebrae, the first five of 

 which bear transverse processes, whilst the terminal ones are very 

 minute and styliform. 



The carpus has an os centrale, and the humerus a well-marked supra- 

 condylar foramen. The clavicles are well-developed, and strongly curved 

 sigmoidally. The manubrium sterni is broad. 



I may, however, take this opportunity of pointing out a useful means 

 of discriminating, in most cases, between the skulls of the Platyrrhine 

 and Catarrhine Monkeys, in addition to the well-known differences in 

 their dentition and in the form of their external auditory meatus. 



In nearly every skull of a New-world Monkey, it will be found that 

 the parietal and malar bones are in contact with each other, for a more 

 or less considerable extent, on the side walls of the skull (vide fig. 5). 

 In the Old-world Monkeys, on the contrary, this contact never (with 

 the exception named below) takes place, the frontal and alisphenoid 

 bones articulating with each other, and so cutting off the connexion 

 between the parietals and malars (vide fig. 6). In the skulls of the 

 genus Hylobates that I have examined this isthmus is very narrow, so 

 that the parietals and malars approach much nearer each other than is 

 usually the case in the Catarrhini ; indeed, in one specimen in the 

 College of Surgeons Museum (5027s) the malar and parietal of one side 

 only touch each other for a very short distance, the frontal and ali- p z g 

 sphenoid not meeting. On the other hand, in all the New-world P- 639 

 Monkeys' skulls that I have examined, the arrangement above described 

 obtains, except in some skulls of the genera Mycetes and Ateles. Thus 



Fig. 5. 



Part of side walls of skull of a New-world Monkey (Brachyurus rubicundus). The 

 parietal (Pa) and malar (Ma) articulate, as in other members of this group. 



