TEETH OF DIPHYODONTS. 321 



Baboons, but in a less degree than in the Orang. The summit 

 of the crown of p 3 terminates in two sharp triedral cusps the 

 outer one rising highest and the second cusp being feebly in- 

 dicated on the ridge extending from the inner side of the first ; 

 the crown has also a thick ridge at the inner and posterior part of 

 its base. The second premolar, p 4, has a subquadrate crown, 

 with the two cusps developed from its anterior half, and a third 

 smaller one from the inner angle of the posterior ridge. Each 

 lower premolar is implanted by two aritero-posteriorly compressed 

 divergent fangs, one in front of the other, the anterior fang 

 being the largest. 



The three true molars are nearly equal in size in the Troglo- 

 dytes Gorilla, the last being a little larger than the first : in the 

 Troglodytes niger, fig. 256, the first, m i, is a little larger than 

 the last, m 3, which is the only molar in the smaller Chimpanzee 

 as large as the corresponding tooth in the black varieties of the 

 human subject, in most of which, especially the Australians, fig. 

 257, the true molars attain larger dimensions than in the yellow 

 or white races. The four principal cusps, especially the two inner 



256 



Teeth of right side, lower jaw, of adult male Chimpanzee, (Troglodytes niger), nat. size. 



ones of the first molar of both species of Troglodytes, are more 

 pointed and prolonged than in Man ; a fifth small cusp is deve- 

 loped behind the outer pair, as in the Orangs and the Gibbons, 

 but is less than that in Man. The same additional cusp is pre- 

 sent in the second molar, which is seldom seen in Man. The 

 crucial groove on the grinding surface is much less distinct than 

 in Man, not being continued across the ridge connecting the 

 anterior pair of cusps in the Chimpanzee. The crown of the 

 third molar is longer antero-posteriorly from the greater develop- 

 ment of the fifth posterior cusp, which, however, is rudimental in 

 comparison with that in the Semnopitheques and Macaques. 



VOL, III. Y 



