lS2 



APES AND MONKEYS. 



yellowish, while the loins, the outer surface of the thighs, and the tip of the tail 

 are reddish chestnut ; the face, hands, and feet being completely black. 



THE BLACK-HEADED UAKARI. 



THE HOWLIXG MONKEYS. 



Genus Mycetes. 



The howling monkeys, or howlers, derive their name from their vociferous 

 cries, which are sufficient in the living condition to distinguish them from all the 

 other American monkeys. To produce this extraordinary noise of which more 

 anon there is a peculiar hollow shell of bone joining on to the upper part of the 

 windpipe, corresponding to the so-called hyoid bone of man, which is a very small 

 and solid structure. The resonance of the voice within this cavity communicates 

 to the cry its peculiar intensity. In order to provide space for this bony shell 

 the sides of the lower jaw-bone are extremely deep, and by this character, as well 

 as by the extreme flatness of the part containing the brain, the peculiar skull may 

 always be recognised. A front view of the head of a howler is given in the wood- 

 cut on the next page, to illustrate the form of the nostrils in the American monkeys. 



The howlers differ from the two preceding groups, and agree with the spider- 

 monkeys and their allies, in having prehensile tails, in which the under surface of 

 the extremity is naked. In addition to the presence of the large bony swelling 

 at the top of the windpipe, they may be at once distinguished from all other 

 prehensile-tailed monkeys by the extreme obliquity of the plane of the face and 



