6o 



THE MONKEYS OF THE NEW WORLD. 



(B) THE MONKEYS OF THE NEW WORLD 



\ (PLATYRRHIN^.)- 



With 36 teeth and broad nasal septum; the nostrils directed sidewards; ischial callosities and 



cheek-pouches always absent. 



To the most essential distinguishing char- 

 acter of these monkeys, that which consists 

 in the number of the teeth, attention was 

 directed in the general account prefixed to 

 the present section (p. 28), where it was 

 pointed out that the New World monkeys 

 have in each jaw one premolar more than 

 those of the Old World, the number of the 

 other teeth remaining the same. 



But the American division is distmguished 

 not only by the number but also by the 

 structure of the teeth as well as of the jaws 

 in general. While in the monkeys of the 

 Old World, more especially in the large 

 baboons, we could establish a decided ten- 

 dency to the carnivorous type of jaws and 

 dentition, we see here on the contrary a 

 development from the lower and small species 

 based on the type of the Insectivora, and that 

 in so marked a manner that the lower jaw of 

 a saimiri, for example, could scarcely be dis- 

 tinguished by the structure of its teeth from 

 that of an insectivore. Although the canines 

 are always more or less prominent and fit into 

 opposite gaps, yet they never exhibit a 

 dagger- like form and attain an excessive 

 length, as we find them to do, for example, 

 among the baboons. The tubercles of the 

 molar teeth, in most species blunt and soon 

 rubbed away by use, become indeed sharply 

 pointed in the insect-eating species, but 

 never acquire a cutting edge. The pre- 

 molars, instead of being close set, are often 

 far apart, and show the sharp conical form 

 of the insectivores. 



The muzzle is always short and only 

 slightly protruding, never assuming that re- 

 semblance to the muzzle of a dog which is 

 so characteristic of the baboons. The head 

 appears far more rounded, the facial lies more 

 under the cranial region, and the latter never 

 has so well-marked crests and ridges as in 

 the allied Old World monkeys. The whole 

 form of the head is much more like that of 

 man or rather like that of the young monkeys 

 of the Old World. One might say with perfect 

 justice that the head of the American monkeys 

 is that of one of the Old World monkeys 

 remaining fixed at the stage of childhood. 



It is often difficult to detect the character- 

 istic form of nose in the skull, since many 

 New World monkeys exhibit quite as narrow 

 a bony ridge in the nose as those of the Old 

 World do. But in living animals one cannot 

 fail to observe that the flat nose becomes 

 broader in its cartilaginous parts, and that the 

 nostrils are directed more sideways. Human- 

 like rounded naked ears are never met with; 

 for the most part the ears are thickly covered 

 with hair and drawn out to a point above. 



The form of the body varies. There are 

 very slender and likewise somewhat plump 

 figures among them, and the limbs are some- 

 times rather powerful, sometimes slim; but 

 the limits of these variations are much 

 narrower than in the Old World monkeys, 

 and even if we leave out of account the much 

 greater size of the latter, we never find in 

 America such powerful frames as those of 

 the baboons and the anthropoid apes. 



