CHARACTERS OF ANTHROPOTDEA 555 



the CataiThines and riatyrrhiiies. In the foriner the nostiils k)ok 

 downwartl and are elu.se together : in tlie latter they are separated 

 by a hroad cartilaginous septum, and the apertures are directed 

 outwards. But numerous other points of difference separate these 

 two groups of tiie Monkey tribe. The Catarrliines often have 

 those remarkable ischial callosities, patches of hard skin brightly 

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

 is tlie case, for instance, with the Anthropoid Apes ; tliere are 

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

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

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

 for the Catarrldnes are exclusively denizens of the Old AVorld, 

 while the l*latyrrhines are as exclusively New A\^irld in range. 

 Again, those of tlie Catarrliines which do possess a long tail, 

 such as the members of the genus Cercocelrus, never sliow the 

 least sign of prehensility in tliat tail. The teeth of the Catar- 

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

 If CiPmf M^} = :52. 



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

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

 rliines. The late Mr. W. A^JjjQil)es pointed out that in most of 

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

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

 from coming into contact by the frontals and the alisphenoids. 

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

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

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

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

 tliree molars. 



Not only are these two groups of tlie Primates absolutely 

 distinct at the present day, but tliey liave Ijeen, 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 wdiich underlie the divergences that have 

 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 



