xvn CHARACTERS OF ANTHROPOIDEA 555 



the Catarrhi nes and Platyrrhiries. In the former the nostrils look 

 downward and are close together ; in the latter they are separated 

 by a broad cartilaginous septum, and the apertures are directed 

 outwards. But numerous other points of difference separate these 

 two groups of the Monkey tribe. The Catarrhines often have 

 those remarkable ischial callosities, patches of hard skin brightly 

 coloured ; the tail may be totally wanting as a distinct organ, as 

 is the case, for instance, with the Anthropoid Apes ; there are 

 often cheek pouches, so that, as Mr. Lydekker has remarked, if a 

 Monkey be observed to stow nuts away in its cheeks for future 

 reference, we may be certain that its home is in the Old World, 

 for the Catarrhines are exclusively denizens of the Old World, 

 while the Platyrrhines are as exclusively New World in range. 

 Again, those of the Catarrhines which do possess a 'long tail, 

 such as the members of the genus Cercocebus, never show the 

 least sign of prehensility in that tail. The teeth of Jbhe Catar- 

 rhines are invariably thirty-two in number, the formula being 

 If C^PmfMf = :',:>. 



In the Old -World Apes there is a bony external auditory 

 meatus, which is wanting (as a bony structure) in the' Platyr- 

 rhines. The late Mr. W. A. Forbes pointed out that in most of 

 the New- World forms the parietals and the malars come into 

 contact ; in the Monkeys of the Old World they are hindered 

 from coming into contact by the frontals and the alisphenoids. 

 The Platyrrhines may have the same number of teeth ; this is 

 the case with the Marmosets, but in them there are three pre- 

 molars and two molars ; in the remaining New-World Monkeys 

 there are thirty-six teeth, but of these three are premolars and 

 three molars. 



Not only are these two groups of the Primates absolutely 

 distinct at the present day, but they have been, so far as we 

 know, for a very long time, since no fossil remains of Monkeys 

 at all intermediate have been so far discovered. This has led to 

 the suggestion that the Monkeys are what is termed diphyletic, 

 i.e. that they have originated from two separate stocks of 

 ancestors. It is hard, however, to understand on this view the 

 very great similarities which underlie the divergences that havt- 

 just been mentioned. But, on the other hand, it is equally hard 

 to understand how it is that, having been separated from each 

 other for so long a period, they have not diverged further in 



