THE PRIMATES EXCEPT MAN 127 



I r c I' p 2' M 3- 



The dentition is certainly not yet adapted for a pure fruit or 

 root diet but is that of a more generally omnivorous animal. 

 Turning now to the modern Anthropoids we find both large 

 and small varieties. The small Anthropoids or Gibbons are 

 animals weighing about 17 lbs. when adult. The large Anthro- 

 poids are as heavy or heavier than Man. The dental formula 

 in all is: 



2 „ 1 _2 „3 



3 



lf,Cy,P-, 



The Gibbons (Hylobates) are widely distributed over Further 

 India and the Malay Archipelago. They are light arboreal 

 apes with disproportionately long arms by means of Avhich they 

 swing themselves from branch to branch. Among the numerous 

 species considerable variations occur in teeth and jaws. Differ- 

 ences are to be found also between members of the same species 

 and of the same sex. 



The specimen figured (Fig. 45) is a young male approaching 

 maturity; the third molar is not yet erupted but the details of 

 the teeth are very clearly shown. The species is rather special- 

 ized and illustrates to what extent Gibbons have deviated from 

 the central primitive type represented by Propliopithecus. 



The diet of the Gibbon is essentially omnivorous although 

 with a large preponderance of roots, shoots and fruits: indeed 

 some species live almost entirely upon herbivorous food. 



The mandible is not powerful and on the skull the weakness 

 of the zygomatic arches is also striking. The muzzle is elon- 

 gated but the incisors have retained their almost vertical posi- 

 tion. The rows of the teeth are nearly parallel and apt to be 

 inturned at their hinder extremities. There is no definite ' ' ape- 

 shelf" and the tongue space between the anterior teeth is not 

 greatly encroached upon by bone. The upper incisors slope for- 

 ward, the lateral ones being somewhat pointed. The canines are 

 long saber-like teeth and the upper is much longer than the 

 lower. The upper premolars are bicuspid and set rather more 



