THE GREAT CHIMPANZEE. 387 



longitudinal rising at their middle part. The lower canine shows the same relative 

 superiority of size as the upper one compared with that in the female Chimpanzee. The 

 canine almost touches the incisor, hut is separated by a diastema one line broad from 

 the first premolar. This tooth is larger externally than the second premolar, and is 

 twice the size of the human first premolar ; it has a subtrihedral crown, with the ante- 

 rior and outer angle produced forwards, slightly indicating the peculiar feature of the 

 same tooth in the Baboons. The summit of the crown terminates in two sharp trihedral 

 cusps, the outer one rising highest, and the second cusp being feebly indicated on the 

 ridge extending from the inner side of the first : the crown of the first has a thick ridge 

 at the inner and posterior part of its base. The second premolar 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. Both the lower premolars are implanted by 

 two antero-posteriorly compressed divergent fangs, the anterior one being the largest. 

 The three true molars are almost equal in size, the first being very little larger than 

 the last, which is the only molar as large as the corresponding tooth in the black 

 varieties of the human subject*, in most of which, especially the Australians, the true 

 molars attain larger dimensions than in the yellow or white races. The four principal 

 cusps, especially the two inner ones, of the first molar of the Chimpanzee are more 

 pointed and prolonged than in Man : a fifth small cusp is developed behind the outer 

 pair, as in- the Orangs and the Gibbons, but is less than that in Man. The same 

 additional cusp is present 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 development 

 of the fifth posterior cusp, which however is rudimental in comparison with that in the 

 Seranopitheques and Macaques. All the three true molars are supported by two 

 distinct and well-developed antero-posteriorly compressed, divergent fangs, longitudi- 

 nally excavated on the sides turned towards each other. The molar series in both jaws 

 forms a straight line, with a slight tendency in the upper jaw to bend in the opposite 

 direction to the well-marked curve which the same series describes in the human 

 subject. 



In the skull of a male Troglodytes niger (Plates LVIII. LIX. & LX.) in which all the 

 teeth and especially the canines had been moderately worn, the cranium is not so much 

 larger proportionally than the female's as it is in the male of the Pithecus Wurmbii, neither 

 are the zygomatic nor the cranial cristas so much more developed. The temporal ridges 

 (PI. LIX. ii) converge more rapidly from the ectorbital processes (12), and meet two 

 inches behind the glabella, forming a low single sagittal ridge ("), extending back- 

 wards in one specimen for an inch and a half, and then dividing again and curving out- 

 wards to the better-developed lambdoid and mastoid ridges (fig. 1,8); whilst in another 



* See my Odontography, Tl. CXIX. fig. 2 m. 



