CHAP. Vl] THE DENTAL SYSTEM OF THE PRIMATES 243 



Nycticebus (Lemuridae). In this form (as in the Slender Loris) the molar 

 teeth of the upper jaw are four-cusped, the cusps being arranged in two 

 pairs, with an oblique ridge joining the antero-inteni.il to the postero- 

 external cusp. This arrangement is met with rarely among the Gebidae, 

 entirely lost in the Cercopithecidae, but reappears in the Simiidae and 

 Hominidae, where it is a marked feature. 



TARSII. Tarsius spectrum (Figs. 163, 164). 



The dentition as a whole is decidedly primitive or archaic 1 . The upper 

 canine tooth is smaller than its lower representative, and in point of actual 

 form, the incisors, canine and first premolar teeth do not greatly differ from 

 each other, for all are of a simple peg-like shape. The upper molar teeth 

 bear three cusps each (" tritubercular " type). 



The lower canines exceed in size those of the upper set. Each of the 

 lower molar teeth bears three cusps, behind which a supplementary "heel" (or 

 "talonid") is situated (the " tuberculo-sectorial " type). 



ANTHROPOIDEA. Cebidae. Cebus capucinus. 



Dental formula of the family : i, | ; c, \ ; pm, § ; m, f . 



The upper teeth : the canine teeth (Fig. 165) are relatively enormous in size, 

 especially in the male sex (cf. Fig. 21) ; the post-canine teeth present a feature 

 of marked contrast with the corresponding teeth of the Lemuridae, inasmuch 

 as the crowns appear much reduced in the antero-posterior direction (this is 

 even more distinct when the lower series are compared, cf. Figs. 162 and 166). 

 A diastema is present. The premolar teeth are three in number and bicuspid, 

 with anterior and posterior cusps: in size they diminish progressively back- 

 wards. Of the three molar teeth, the first is the largest and the diminution 

 in size backwards is very rapid, the last tooth being minute. The molar teeth 

 bear four cusps, two outer and two inner, and in the species under considera- 

 tion (C. capucinus) no connecting ridges are seen. In some forms the antero- 

 internal and postero-external cusps may be connected by an oblique ridge 

 (cf. Fig. 165). 



The lower canine teeth correspond to the upper teeth in size, and in closing 

 they pass anteriorly to these as in the great majority of Eutheria. The first 

 of the three premolar teeth is pyramidal and suggests a transition from the 

 canine form to the bicuspid premolar form: it bears one predominant cusp 

 and a second smaller cusp, and is distinctly larger than the two remaining 

 premolar teeth, which are bicuspid with external and internal cusps, and sub- 

 equal in size. The three molar teeth diminish rapidly in bulk backwards, the 

 last being clearly degenerate, and this degeneracy in the third molar tooth of 

 the otherwise comparatively primitive Cebidae must be insisted on. Such 



1 Cf. Hubrecht, Descent of the Primates, 1897, p. 11. Earle, Natwal Science, 

 May 1897, p. HOV> (with especial reference to the researches of Professor Leche). 



16—2 



