CHAPTEE VIII 



THE TEETH OF MAMMALS (Continued) 



The Ungulata is that great division of hoofed 

 quadrupeds which are herbivorous in food habits 

 and form the other extreme as opposed to the 

 carnivorous animals. There are two great divi- 

 sions of the Ungulata, — first, the Artiodactyla, 

 the even-toed Ungulates (the Ox, Deer, Sheep, 

 Pig, etc.), and second, the Perissodactyla, the odd- 

 toed Ungulates (the Horse, Rhinoceros, Tapir, 

 etc.). The dental system of this great branch 

 presents extreme modification for adaptation to 

 an exclusively vegetable diet, and is highly elab- 

 orated and complex. It is the extreme of special- 

 ization in the herbivorous direction. The molar 

 teeth are of the folded or lophodont type, the tis- 

 sues being folded on the sides of the crown and 

 the valleys dipping down into the crown so as to 

 form high, sharp crests which, when worn away, 

 present curious patterns of the arrangement of 

 the dental tissues (Fig. 63). As opposed to the 

 vertical direction of the movement of the jaw in 

 the Carnivora, in this order the jaw movement is 

 horizontal, the articulation being wide and loose, 



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