130 MAMMALIAN DENTITION 



backward in the male. The "ape-shelf" can be clearly seen 

 jutting backward from the symphysis and the anterior part of 

 the tongue space is encroached upon by bone. The palate, as 

 in other Anthropoids extends behind the last molar tooth. 



The lower incisors are almost vertical but those of the upper 

 jaw slope forward. The canines are much larger in the male, 

 the upper being a little longer than the lower. The upper pre- 

 molars are bicuspid and in the male set rather within the line 

 of the molars. The lower first premolar is sectorial but not 

 markedly so; the second is molariform. Of the lower molars 

 the second is the largest, the third may or may not be smaller 

 than the first. In the upper molars there is a typical trigon 

 with the oblique ridge connecting protocone and metacone 

 but there is also a well-marked hypocone which tends to be 

 somewhat smaller in the third molar than in the others. In 

 the lower molars the hypoconid is rather small but still by its 

 approximation to the large metaconid separates the other two 

 main cusps. The hypoconulid is present on all the molars and 

 is placed well towards the lateral side. 



The Chimpanzee (Fig. 47), an Anthropoid about as heavy as 

 Man, is in many respects more man-like than the Gorilla and 

 the teeth have developed certain secondary features also found 

 in our own dentition. The jaws are very similar to those of 

 the Gorilla. The mandible is strong with a moderately deep 

 body. A symphysial region and "ape-shelf" occur as in 

 Gorilla. The tooth rows are almost parallel in the female but 

 diverge forward in the male. 



The lower incisors are nearly vertical and the uppers gently 

 sloping. The canines are large and project somewhat laterally 

 as in Gorilla. The upper premolars are bicuspid and set a lit- 

 tle within the line of the molars ; the lower first is sectorial in 

 appearance and the second molariform. In the molars the 

 cusps are more nipple-shaped than in Gorilla and the crowns 

 show numerous variously arranged tiny grooves or crenations 

 obscuring to some extent the original cuspidation. This crena- 



