206 MAMMALIAN DENTITION 



habit. The last lower molar has a talonid extended some- 

 what by the addition of an extra cusp but this cusp is smaller 

 than is the case usually among the Pecora. In addition to the 

 overlapping upper molars, the extension of the last lower molar 

 and the general hypsodont character of the teeth there is an- 

 other feature in which the dentition of the Camel resembles 

 that of the Pecora. This is the relative narrowness of the 

 mandible compared with the breadth of the palate. In conse- 

 quence the upper and lower cheek teeth of one side only can 

 enter into contact at one time: on the opposite side the upper 

 cheek teeth project so far beyond those of the lower jaw that 

 there can be no occlusion. Thus the Camel like the Deer and 

 the Cow masticates first upon one side of the mouth and then 

 upon the other. 



PECORA 



The Pecora or true Ruminants, all of them browsing or 

 grazing animals of Old- World origin, are the most specialized 

 and varied of the Artiodactyla. All are alike in the absence of 

 upper incisors and, with the exception of some Deer, of the 

 upper canines also. The lower canines are always incisiform; 

 the number of premolars three in each jaw and the molars 

 invariably selenodont. The usual four cusps are present on 

 the crown of each upper and each lower molar as in the Camel. 

 The paraconid alone is lost. The last lower molar presents an 

 additional cusp on the talonid, relatively larger than that pres- 

 ent in the Camel, thus exhibiting, as previously observed, a 

 typical herbivorous specialization. But this additional cusp is 

 not invariable in the Pecora: it is absent in Salt's Antelope one 

 species of the genus Neotragus, and is rudimentary in other 

 species of this genus and in the Gnus. 



The Pecora are subdivided into the solid-horned type or 

 Cervicornia comprising the Deer and Giraffes, and the hollow- 

 horned or Cavicornia including Antelopes, Sheep, Goats, Oxen 

 and Buffaloes. The latter group is of comparatively recent 



