THE TEETH OF PROBOSCIDEA. 363 



greater bulk of the tooth, the roots are comparatively in- 

 significant, and the interspaces of the cusps are filled up 

 with cementum. The molar of the Indian elephant con- 

 sists of a larger number of yet more elongated and flattened 

 cusps, so that the greater part of the tooth is made up of 

 these flattened plates, fused together with cementum, and so 

 forming a strong and solid mass ; the roots are compara- 

 tively inconspicuous. 



When the tooth is a little worn each plate consists of an 

 area of dentine surrounded by enamel. The interspaces 

 of the series of plates are wholly filled up by cementum ; 

 the summits of each plate were originally maminillated, 

 and divided up into more numerous blunt processes than 

 the corresponding parts of the tooth of a Mastodon ; when 

 the tooth comes into use the rounded tips are soon worn 

 off, and the grinding surface of the tooth then consists of 

 narrow transverse bands of dentine, surrounded by enamel, 

 and of cementum in their interspaces. The difference in 

 hardness between these three tissues preserves a constant 

 rough surface, owing to their unequal rate of wear. In 

 their wild condition elephants eat trees with succulent juicy 

 stems, and oftentimes grass torn up by the roots, from 

 which they roughly shake out the adherent earth. In con- 

 finement, the food containing less that is gritty, the teeth 

 become polished by working against one another, but the 

 rate of wear is insufficient to keep their surfaces rough ; for 

 the softer cementum does not get worn down in the inter- 

 spaces of the plates of dentine and enamel, but remains on 

 a level with them. 



Great though the size of the Proboscideans be, they have 

 some points of affinity with the Rodents in the great 

 development of the incisors, the vacant interval between 

 these and the molar teeth, and, as was pointed out by the 

 late Professor Rolleston, the enamel of the elephant's molar 

 having, in its inner portions, a pattern produced by the 



