TEETH OF ORANG AND CHIMPANZEE. 803 



orang. The characteristics of the human incisors are, in 

 addition to their true incisive wedge-like form, their near 

 equality of size, their vertical or nearly vertica^position, 

 and small relative size to the other teeth and to the en- 

 tire skull. The diastema, between the incisors and the 

 canine on each side, is as well marked in the male chim- 

 panzee as in the male orang. The crown of the canine 

 (lb.), c, passing outside the interspace between the lower 

 canine and premolar, extends, in the male Troglodytes 

 gorilla, a little below the alveolar border of the under 

 jaw when the mouth is shut: the canines in both jaws 

 are twice the size of those teeth in the female gorilla. 



Both premolars are bicuspid; the outer cusp of the 

 first and the inner cusp of the second being the largest, 

 and the first premolar consequently appearing the largest 

 on an external view. The anterior external angle of the 

 first premolar is not produced as in the orang, which, in 

 this respect, makes a marked approach to the lower quad- 

 rumana. In man, where the outer curve of the premolar 

 part of the dental series is greater than the inner one, the 

 outer cusps of both premolars are the largest ; the alter- 

 nating superiority of size in the chimpanzee accords with 

 the straight line which the canine and premolars form 

 with the true molars. 



The three true molars are quadricuspid, relatively 

 larger in comparison with the bicuspids than in the 

 orang. In the first and second molars of both species of 

 chimpanzee, a low ridge connects the antero-internal with 

 the postero-external cusp, crossing the crown obliquely, 

 as in man. There is a feeble indication of the same ridge 

 in the unworn molars of the orang ; but the four princi- 

 pal cusps are much less distinct, and the whole grinding 

 surface is flatter and more wrinkled than in the cliim- 



