386 PROFESSOR OWEN ON THE OSTEOLOGY OF 



the interspace between the lower canine and premolar, extends in the male Troglodytes 

 niger a little below the alveolar border of the under jaw when the mouth is shut : the 

 seventh character*, therefore, of the genus, ' apices of canines lodged in intervals of the 

 opposite teeth,' when tiie mouth is closed, is applicable only to the female, and does not 

 distinguish Troglodytes from Pithecus. The upper canine of the male Troglodytes niger 

 is conical, pointed, but more compressed than in the Orang, and with a sharper poste- 

 rior edge ; convex anteriorly, becoming flatter at the posterior half of the outer surface, 

 and concave on the corresponding part of the inner surface, which is traversed by a 

 shallow longitudinal impression : a feeble longitudinal rising and a second linear im- 

 pression divide this from the convex anterior surface, which also bears a longitudinal 

 groove at the base of the crown. The canine is rather more than twice the size of that 

 in the female. Both premolars {ih. \ p, 2 p, PL LX.) are bicuspid ; the outer cusp of the 

 first and the inner cusp of the second being the largest, and the first premolar conse- 

 quently appearing the largest on an external view (PL LVIIL). The difference is less 

 marked in the female. The anterior external angle of the first premolar is not pro- 

 duced as in the Orang. 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 alternating superiority of size in the Chimpanzee accords with the straight 

 line which the canine and premolars form with the true molars. 



The true molars (PL LX. 1 ?n, 2 m, 3 m) are quadricuspid, relatively larger in com- 

 parison with the bicuspids than in the Orang : the last is the smallest by the feeble 

 development of the two bind cusps. In the first and second molars 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 principal cusps are much less distinct, and the whole grinding 

 surface is flatter and more wrinkled, than in the Chimpanzee. A low ridge girts the 

 base of the autero-internal cusp of each of the upper true molars in the male Chim- 

 panzee : it is less marked in the female. The premolars as well as molars are severally 

 implanted by one internal and two external fangs, diverging but curving towards each 

 other at their ends as if grasping the substance of the jaw. The two outer fangs of the 

 second premolar are connate in one female specimen. 



In the lower jaw the lateral incisors are broader than the middle ones, but have their 

 outer angle rounded off ; they are all much larger and less vertically implanted than in 

 Man (Pis. LVIIL & LIX.). The lower canines are two inches in length, including the 

 root ; the enamelled crown is three-fourths of an inch in length, and two-thirds of an inch 

 across the base ; it is conical and trihedral ; the outer and anterior surface is convex, 

 the other two surfaces are flattened or subconcave, and converging to an almost tren- 

 chant edge directed inwards and backwards; a ridge separates the convex from the 

 antero-internal flat surface ; both this and the posterior surface show slight traces of a 



* Zool. Trans, vol. i. p. 372. 



