250 THE DENTAL SYSTEM OF THE PRIMATES [SECT. A 



of the premolar teeth in Chimpanzee are very similar to those of the same 

 teeth in Gorilla, though in the Chimpanzee these teeth are distinguished 

 chiefly by their smaller size and the persistence of crenate markings. Very 

 similar remarks apply to the lower molar teeth, viz., that they resemble the 

 corresponding teeth in Gorilla, but present crenate foldings of the enamel, 

 and are less elongated in the antero-posterior direction. In comparison with 

 the human teeth of the mandibular series, it is to be noted that the Chim- 

 panzee does not provide the marked contrast in size between the second 

 premolar and the first molar. The characteristic appearances are shewn in 

 Figs. 176 and 177 respectively. 



ANTHROPOIDEA. Homtnidak. Homo sapiens. 



Dental formula as in all the Catarrhine Primates : i, |; c, ^; pm, # ; m, §. 

 (Figs. 178, 179.) 



It has been already remarked that the dentition of the Chimpanzee 

 provides in many ways a transition from the simian to the human modification 

 of the Primate type. When the human dentition is examined in series with 

 those of the other Primates, perhaps the most striking and peculiar feature 

 is the reduction in size of such teeth as are situated anteriorly to the molars, 

 viz., the premolars, canines, and incisors. This reduction is doubtless associ- 

 ated with the change in function determined by the greater freedom of the 

 upper limb in man, whereby the jaws are relieved, to a larger extent than 

 in any other Primate animal, of their prehensile function. Again, the dis- 

 tinctive characters of the dentition are correlated with the modifications of 

 the cranial base to which reference has been made in the preceding chapter. 



The canine teeth have almost entirely lost the predominance in size that 

 obtains in the majority of the Primates : and the diastema is no longer 

 present, except as an anomaly. 



The upper premolar teeth are bicuspid and possess a single root, the molar 

 teeth being furnished with three roots, which are however in the majority 

 of the Hominidae, not divergent, but parallel, and in the third molar may be 

 reduced to two, which may even be fused into a single pegdike root. 



The molar teeth do not present crenate markings in the adult : in size, 

 the second upper tooth is the largest, next to this the first molar tooth, while 

 the last tooth is practically always degenerate, and may be absent. The 

 upper molar cusps are four in number, disposed as in the Simiidae but 

 commonly less prominent. The oblique ridge is distinct in the two foremost 

 teeth, but often obscure, or absent from the last tooth. 



In the mandible the first premolar is often nearly as large as the canine 

 tooth, and larger than the second premolar tooth : both are bicuspid and 

 furnished with single roots. The second lower premolar is much smaller than 

 the first molar. At this point therefore a remarkable change in size is 

 evident. Herein the human dentition differs from that of the three larger 

 Simiidae (cf. Figs. 173, 175, 177, 179). The molar teeth present varying 



