THE PRIMATES EXCEPT MAN 133 



crenations already noted in less pronounced form in the Chim- 

 panzee. The upper premolars are bicuspid teeth; the first lower 

 shows a more pronounced sectorial character than in any other 

 Anthropoid since it is tilted backward and the enamel clothes 

 the upper part of the anterior root ; the second lower premolar 

 may be quite molariform in appearance. In the molar series 

 the second is the largest and the third, especially in the man- 

 dible, tends to be of considerable size. The cusps are so low as 

 to be almost indistinguishable in many cases. In the upper 

 molars the trigon, the oblique ridge and the hypocone can all 

 be made out except in the last in which crenations make the 

 outlines very obscure. In the lower molars which are elongated 

 though not so markedly as in the Gorilla the approximation of 

 hypoconid and metaconid causes separation of the two other 

 principal cusps. The hypoconulid present on all the teeth lies 

 axially or to the outer side. 



Having now discussed in detail the dentitions of the various 

 Anthropoid Apes so far as the jaws and ctoayiis of the teeth 

 are concerned it will be advantageous to recapitulate several 

 important features before passing on to the teeth of Man. Dis- 

 cussion of the roots of the Anthropoid teeth and of the milk 

 dentition will be taken up in later chapters. 



The mandible has a broad ramus and a body only moderately 

 deep, the height of which shows more or less sudden increases 

 in the premolar region and between the lateral incisor and 

 canine. The symphysial region slopes backward especially in 

 the male and an "ape-shelf" is present in varying degree ex- 

 cept in certain Gibbons. The palate extends well back of the 

 last molars especially in some Gibbons and in the male Gorilla 

 and Orang. In all the muzzle is elongated. 



The incisors are set in an arch betAveen large and powerful 

 canines beyond which the cheek teeth are arranged in rows 

 almost parallel in the Gibbons and the females of the large 

 Anthropoids but diverging forAvard in the male Chimpanzee, 

 Gorilla and Orang. The antero-posterior axes of the molars 

 of both jaAvs are in the same straight line or form an angle 



