THE SKELETON IN MAMMALIA. THE TEETH. 



421 



human incisors, or may, as in those of Rodents, be brought 

 about by the more rapid wearing away of the posterior edge, 

 the anterior edge being hardened by a layer of enamel. 



m.c 



m 2 



pnr4 



FIG. 81. SKULL OF A YOUNG INDIAN EHINOCEBOS (R. unicornis), 



SHOWING THE CHANGE OF THE - DENTITION X \. (Brit. MllS.) 



1. nasal. 



2. frontal. , 



3. parietal. 



4. zygomatic process of squa- 



mosal. 



5. jugal. 



wiJT milk incisor. 



inc. milk canine. 



mpm r milk premolar. 



I r first incisor. 



c. canine. 



pm 2 , pm s , pm^. 2nd, 3rd and 



4th premolars. 

 ?!, w 2 . first and second molars. 



Then, again, the crown may, as in the majority of grinding 

 teeth, be' more or less flattened. The various terms used in 

 describing some of the forms of the surface of grinding teeth 

 are denned on page 345. 



The teeth of the Aard Varks are compound, and differ 

 completely from those of all other mammals (see p. 425). 



As a rule, the higher the general organisation of an anima] 



