THE TEETH OF MAMMALS 



121 



being exposed to wear. The teeth are of contin- 

 uous growth, and are usually monophyodont. 

 Many of this order feed only on insects, the long 

 whip-like tongue being covered with a viscous 

 mucus to which the insects — principally ants — 

 adhere. For this simple diet the teeth are re- 

 duced and degenerate in form and structure. 

 The upper teeth are usually confined to the maxil- 



FlG. 39. — Roentgenogram of teeth of Armadillo (Euphr actus minutus). 



lary bones only, the premaxillaries being desti- 

 tute. In the Cape Ant-eater, the teeth are all 

 molar-like in form, increasing in size from front 

 to back. They are oval on section, and two facets 

 are produced by wear as the teeth in the upper 

 and lower series alternate on striking. The for- 

 mula is m. 2=£ = 26. The Armadillos (Figs. 26 

 and 39) are peculiar for the shell-like covering in 

 which the animals roll up, when attacked, for pro- 



