THE TEETH OF MAMMALS 



137 



table fiber on which it feeds. The Hares and 

 Rabbits have the formula, — 



. 2-2 0-0 3-3 3-3 OQ 



l. — - c — p.m. — m. — - = 28. 

 2-2 0-0 P 2-2 3-3 



Fig. 46. — Teeth of Squirrel (Seurius niger). 



In most species of this family there is a second 

 incisor posterior to the central (Fig. 45). The 



F 



■j 



R 





'■■' . 



J 



l&^tf 



Itt^ 



li 



Fig. 47. — Mandible of Squirrel (Seurius niger), showing incisor, pre- 

 molars, and molars. 



npper centrals have vertical grooves upon the an- 

 terior face which are also characteristic. The 

 molars are remarkable for their great length, and 



