PECORA 



generally be distinguished, inasmuch as the true molars of the Cervulce 

 are more or less brachydont, and those of the JBovidce generally 

 hypsodont, i.e. the teeth of the former have 

 comparatively short crowns (Fig. 122), which, 

 -as in most mammals, take their place at once 

 with the neck (or point where the crown and 

 root join) on a level with or a little above the 

 alveolar border, and remain in this position 

 throughout the animal's life ; whereas in the 

 other forms (Fig. 1 2 3), the crown being lengthened 

 and the root small, the neck does not come up FIO. 122. Crown sur- 

 to the alveolar level until a considerable part fac f of " rn left "Pi** 



.... ,. * molar of Palceomeryx siva- 



oi the surtace has worn away, and the crown of unsis, to show brachydont 



the tooth thus appears for the greater part of type. (From the 

 the animal's life partially buried in the socket. WM ' 

 In this form of tooth (which is almost always most developed 

 in the posterior molars of the permanent series) the constituent 

 columns of the crown are necessarily nearly parallel, whereas 



CT FIG. 123. Inner and outer aspects of an almost unworn left upper molar of the Nilghai 

 (Boselaphus tragocamdus), to show hypsodont type. (From the Palasontologia Indica.) 



in the first-described they diverge from the neck towards the free 

 or grinding surface of the tooth. In the completely hypsodont 

 form the interstices of the lengthened columnar folds of enamel 

 and dentine are filled up with cement, which gives stability to 

 the whole organ, and is entirely or nearly wanting in the short- 

 crowned teeth. The same modification from low to high crowns 

 without essential alteration of pattern is seen in an even still 

 more marked manner in some of the Perissodactyle Ungulates, 

 the tooth of the Horse bearing to that of Anchitherium the same 

 relation as that of an Ox does to the early selenodont Artiodactyles. 



