APES. 447 



molars (ib. m.) are almost equal, the first being smaller or not 

 larger than the last ; which is the only molar equalling in size the 

 corresponding tooth in the black varieties of the Human subject 

 (PL 1 19, fig. 2, m.), in which the true molars attain their largest 

 dimensions. 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 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 connect- 

 ing 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 rudi- 

 mental in comparison with that in the Semnopitheques and Ma- 

 cacques. All the three true molars are supported by two distinct 

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

 longitudinally 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. 



172. Succession and Structure. — The deciduous dentition in- 

 cludes in all the catarhine Quadrumana, twenty teeth, viz : 



Incisors — : canines — : molars - — : = 20. 



2—2 ' 1—1 ' 2-2 



The second deciduous molar is quadri- cuspid, and is succeeded by 

 a permanent premolar with a bicuspid crown ; the first deciduous 

 molar is bicuspid, and in the lower jaw of the Baboons it has 



contrary in PI. 119, fig- Ij m.) He proceeds — "Quant aux alveoles des dents de ces 

 Singes superieures, il est aise de voir qu'elles doivent presenter quelques differences concor- 

 dantes ; ainsi a la machoire superieure, a peine si les deux trous externes sont indiques 

 pour la premiere et surtout pour la seconde des avant molaires, aussi bien chez le Chim- 

 panzee que chez I'Orang-Outang. Les differences sont moins marquees pour les autres 

 molaires et surtout a la machoire inferieure," p. 47. If there ever was an anatomical 

 comparison deserving a deeper and more decisive examination it is that regarding the 

 mode of implantation of the teeth of the Chimpanzee and Orang, which bears so imme- 



