630 MANUAL OF ZOOLOGY. 



also is usually opposable to the other digits, so that the animal 

 becomes truly quadrumanous, or four-handed. 



The incisor teeth generally are - , and the molars ^7^ 



with broad and tuberculate crowns. Perfect clavicles are pre- 

 sent. The teats are two in number, and are pectoral in posi- 

 tion, and the placenta is discoidal and deciduate. 



The Quadrumana are divided by Owen into three very 

 natural groups, separated from one another by their anatomical 

 characters and by their geographical distribution as follows : 



Section A. Strepsirhina. The members of this section are 



Fig. 270. Green Monkey or Guenon (Cercocebus sabceus) after Cuvier. 



characterised by the nostrils being curved or twisted, whilst 

 the second digit of the hind-limb has a claw. This section 

 includes the true Lemurs and a number of allied forms. It is 

 chiefly referable to Madagascar as its geographical centre ; but 

 it spreads westwards into Africa, and eastwards into the Indian 

 Archipelago. 



Section B. Platyrhina. This section includes those Quad- 

 rumana in which the nostrils are placed far apart ; the thumbs 

 of the fore-feet are either wanting, or, if present, are not oppos- 

 able to the other digits ; and the tail is generally prehensile. 



