AGE OF ANIMALS. 205 



" At eleven years the corner teeth are rounded, and the 

 central enamel becomes very narrow. 



" At twelve years the nippers are all rounded, and the cen- 

 tral enamel has entirely disappeared from the lower jaw ; 

 but it may still be seen in the upper jaw. 



"At thirteen years the middle nippers commence to as- 

 sume a triangular form in the lower jaw, and the central 

 enamel has entirely disappeared from the corner teeth of the 

 upper jaw. 



" At fourteen years the middle nippers have become tri- 

 gular, and the second pair are assuming that form ; the cen- 

 tral enamel has diminished in the middle nippers of the up- 

 per jaw. 



" At fifteen years the second pair have become triangular 

 (fig. D) ; the central enamel is still visible in the upper jaw. 



FIG. D. 



" At sixteen years all of the teeth in the lower jaw have 

 become triangular, and the central enamel is entirely re- 

 moved from the second pair in the upper jaw. 



" At seventeen years the sides of the triangle of the mid- 

 dle nippers are all of the same length ; the central enamel 

 has entirely disappeared from the upper teeth. 



