ORDERS OF MAMMALIA. 357 



which the nostrils are simple, and are placed far apart ; the thumbs 

 of the fore-feet are wanting, or, if present, are hardly opposable ; 

 and the tail is generally prehensile. The Platyrhine Monkeys are 

 exclusively confined to South America, occurring especially in 

 Brazil, and they are all adapted for a more or less purely arboreal 

 life. The best-known members of this section are the Marmosets 

 {Hapalidce), and the great family of the Cebidce, comprising the 

 Spider-monkeys, the Howlers, and others. The Howlers {Mycetes) 

 are remarkable for having a bony drum at the summit of the wind- 

 pipe, by which the voice is rendered extraordinarily resonant, and 

 peculiarly weird and terrifying to those who hear it. 



As regards their dentition, the Platyrhine Monkeys differ from 

 the Old World Monkeys, as also from Man, in having an additional 

 prsemolar on each side of each jaw. They have, therefore, three 

 prsemolars on each side of each jaw, instead of only two. On the 

 other hand, they have either three molars on each side, as have the 

 Old World Monkeys and Man, or they have only two. The dental 

 formula of the Marmoset is — 



.2—2 1—1 3—3 2—2 .,-, 



I — : c : pm ; m =32. 



2—2' 1—1 ' ^ 3-3' 2—2 



The dental formula of the Howlers {Mycetes) is — 



.2—2 1—1 3—3 .3—3 „„ 



I ; c ; pm ; m =36. 



2—2 1—1 ^ 3—3 3—3 



Section C. CatarJdna. — In this, the highest section of the Qicadru- 

 mana, the nostrils are oblique and placed close together, and the 

 thumbs of all the feet are opposable, so that they are truly " quadru- 

 manous." The dental formula agrees with that of Man ; — 



.2—2 1—1 2—2 3—3 „., 



I — ■ c ; ptn — ; m — =.5z. 



2—2 1—1 ^ 2—2 3—3 



The incisor teeth, however, are prominent and projecting, and the 

 canines, especially in the males, are large and pointed, whilst the 

 teeth form an uneven series. The tail is never prehensile, and is 

 sometimes absent. Cheek-pouches are -often present. In one single 

 instance (Colobtis) the thumbs of the fore-limbs are wanting. 



With the single exception of a Monkey which occurs on the Rock 

 of Gibraltar, all the Catarhine Monkeys are confined to Africa and 

 Asia. The most typical forms of the section are the Semnopitheci 

 and Macaques of Asia. Less typical are the Baboons, which inhabit 

 Africa, and are amongst the most repulsive of all the Quadrumana. 

 In these the tail is always short, and often quite rudimentary. The 

 head is large, and the muzzle greatly prolonged, having the nostrils 

 at its extremity. The skull (tig. 262) is furnished with great bony 



