188 COMPARATIVE DENTAL ANATOMY 



grinding surface is finely wrinkled. The lower 

 molars have five tubercles, three externally and 

 two internally. The third is five-lobed, with a 

 wrinkled face. 



The Chimpanzee is a medium-sized man-ape 

 found in West Africa. The dentition is strictly 

 quadrumanous, but approaches the human type in 

 many particulars. 



The central incisors are reduced from those of 

 the Orang, so that they are smaller and the lat- 

 erals larger than in the latter ape, which is a 

 lower form. Each incisor has a prominent basal 

 ridge. The laterals are larger, but still have the 

 distal corners rounded off. The lower incisors 

 are large, and project forward. 



The diastema between the incisors and canines 

 is narrower than in the Orang. 



The canine is much smaller than in the Orang, 

 is conical, and with a sharp posterior edge. It 

 does not erupt until after the third molar is in 

 place. In the female, it follows the second molar, 

 and is much smaller. As in the Orang, it is so 

 long as to extend below the lower alveolar border 

 when the mouth is closed. The lower canines are 

 smaller, conical, and trihedral, and with a sharp 

 inner edge. 



Both upper premolars are biscuspid, the ex- 

 terior cusp being most pronounced. The lower 

 first premolar is larger than the second, and is 



