VII MONKEYS— AFFINITIES AND DISTRIBUTION 167 



of the tongue and being an outgrowth of the hyoid bone, 

 with an opening into the windpipe by which the animal 

 can force air into it. This increases the j)ower of its 

 voice, acting something like the hollow case of a violin, 

 and producing those marvellous rolling and reverberating 

 sounds which caused the celebrated traveller Waterton 

 to declare that they were such as might have had their 

 origin in the infernal regions. The howlers are large and 

 stout-bodied monkeys with bearded faces, and with very 

 strong and powerfully grasping tails. They inhabit the 

 wildest forests ; they are very shy, and are seldom taken 

 captive, though they are less active than many other 

 American monkeys. 



Next come the Spider-Monkeys (genus Ateles), so called 

 from their slender bodies and enormously long limbs and 

 tail. In these monkeys, the tail is so long, strong, and 

 perfect, that it completely takes the place of a fifth hand. 

 By twisting the end of it round a branch the animal can 

 swing freely in the air with complete safety ; and this 

 gives them a wonderful power of climbing and passing 

 from tree to tree, because the distance they can stretch 

 is that of the tail, body, and arm added together, and 

 these are all unusually long. They can also swing them- 

 selves through the air for great distances, and are thus 

 able to pass rapidly from tree to tree without ever de- 

 scending to the ground, just like the gibbons in the 

 Malayan forests. Although capable of feats of wonderful 

 agility, when needful, the spider-monkeys are usually slow 

 and deliberate in their motions, and have a timid, melan- 

 choly expression, very different from that of most 

 monkeys. Their hands are very long, but have only four 

 fingers, being adapted for hanging on to branches rather 

 than for getting hold of small objects. It is said that 

 when they have to cross a river the trees on the opposite 

 banks of which do not approach near enough for a leap, 

 several of them form a chain, one hanging by its tail from 

 a lofty overhanging branch and seizing hold of the tail of 

 the one below it, then gradually swinging themselves 

 backwards and forwards till the lower one is able to seize 

 hold of a branch on the opposite side. He then climbs 



