Monkeys. 119 



hand is not well developed, or is absent as in the 

 spider monkeys : on all their fingers they have thick 

 convex nails. Most of these live in the woods of 

 Brazil, and are found in troops. The howling 

 monkeys have a drum-like enlargement of the tongue 

 bone at the top of the larynx or organ of voice, and 

 with it they can produce a loud booming sound, 

 audible for nearly a mile. In all the American 

 monkeys the nostrils are separated by a very broad 

 partition, their ear-drums or tympanic bones in the 

 skull have also wide oval mouths. 



3. The Old World monkeys and apes are charac- 

 terised by having a narrow nasal septum, and the ear- 

 drums have a long tubular mouth. The dentition is 



similar to that of man, the premolars being - 2 . 



2 2 



They have almost always an opposable thumb on the 

 hand as well as on the foot, though it is rarely as 

 perfect, and the muscle which bends it is never sepa- 

 rate from the common flexor muscle of the other 

 fingers. The baboon family may be known by pos- 

 sessing cheek pouches, and callous patches whereon 

 they sit, as well as by their elongated jaws. The true 

 baboons have dog-like muzzles and very short tails ; 

 they are confined to Africa and Arabia, and some of 

 them have curiously coloured faces; thus the mandrill, 

 with its blue, deeply-grooved cheeks, its brilliant 

 scarlet lips and nostrils, and its white beard, is a 

 most striking-looking creature. Some, like the Bar- 

 bary ape, the only species which now lives in Europe, 

 have no visible tails ; others, like the cercopitheci or 

 green monkeys, have long tails, but these organs are 



