CATARRHINES AND PLATYRRHINES 
in the continents of the old world. This is seen also 
in the monkeys. The American monkeys have the 
nostrils wide apart with a septum between them; the 
tail, when present, is often, indeed nearly always, 
prehensile, and serves the purpose, as it has been 
termed, of a fifth hand, to enable its possessor to grasp 
additionally on to the branch of a'tree. It is not clear 
that the monkeys of America are deafer than their allies 
of Asia and Africa ; but it is an anatomical fact that 
the former have not the little spout-like bone for con- 
veying sound to the internal part of the ear devoted 
to the reception and analysis of sound waves, which is 
present in the Catarrhines. The visitor to the Zoo 
will note the eager way in which monkeys will often 
cram nuts and other proffered food into their cheeks 
to be disgorged later, and eaten at leisure; but it will 
be noted that no monkey hailing from the American 
continent ever does this; there are indeed in the 
Platyrrhines no cheek pouches at all. Nor do those 
gaudy red callosities, so characteristic of baboons and 
other apes of the Old World, ever deck or adorn the 
monkeys of America. 
The Platyrrhine apes of America consist of two main 
groups, which are themselves further apart than are 
any two forms among the apes of the Old World, not 
excepting such apparent contrasts as the gorilla and 
the bonnet monkey. In the tiny little marmosets the 
tail is not prehensile, and the hand is, so to speak, not 
a hand but a paw. The thumb is not opposable to the 
other fingers, and the nails upon those fingers are 
rather claws than nails; but these characteristics are 
obviously so far not ape-like, and ally the marmosets 
to animals lower in the series than apes. These points 
can be readily verified by the visitor. 
The apes of the Old World are usually divided into two 
great groups, the Catarrhinesand the Simiide, or an- 
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