"be the case, the premolars. That the three teeth in question are really milk-molars is 

 proved by the circumstance that in some of the extinct species they were vertically 

 succeeded by teeth of simpler structure corresponding to the premolars of the pig. 



In order to understand the structure of the molar teeth of the elephants, it will 

 be advisable to take those of one of certain extinct species which, like Cliffs ele- 

 phant, exhibit a simpler conformation than those of the existing species. Such a 

 tooth is represented in the accompanying cut, and will be seen to be composed 

 of a number of low roof-like transverse ridges (in this case six), separated by open 

 valleys. When unworn, as on the right side of the figure, such ridges are crowned 

 by a number of small tubercles; but the effect of wear, as shown in the three ridges 

 on the left side of the figure, is to perforate the enamel of which the ridges are ex- 

 ternally composed, and thus to reveal an elliptical surface of ivory surrounded by a 

 narrow border of enamel. In the figured tooth the valleys between the ridges are 

 completely open and devoid of cement, but in the teeth of other species of nearly 

 similar type they contain a certain amount of this constituent. Now it only re- 

 quires that the ridges in a tooth like that of Cliffs elephant should be greatly 

 increased in height, with a concomitant diminution of their basal width, which would 

 admit of a greater number being 

 born in the same length of space, 

 and by the intervening valleys 

 being completely filled with 

 cement, to produce a tooth like 

 that of the Indian elephant. In 

 such a tooth, as shown in the 

 figures on pp. 1 1 14 and 1117, the 

 ridges have become so tall as to 

 assume the appearance of thin 

 and nearly parallel plates, with 

 their investing enamel thrown 

 into a series of fine plications, 



A LEFT UPPER MOLAR TOOTH OF CLIFT'S ELEPHANT. 

 (One-half natural size.) 



or puckers; and the intervening 

 valleys have become so deep- 

 ened and narrowed, that their 

 'contained cement is also in the form of exceedingly thin plates. When worn, as in 

 the figure on p. 1117, such a tooth presents on its surface a series of very narrow 

 ellipses of yellow ivory, surrounded by an elevated rim of the harder white enamel, 

 marked by its characteristic puckers; while between the ellipses of enamel-bordered 

 ivory come the layers of cement. The succession of layers in such a tooth is there- 

 fore arranged in the following order, viz., cement, enamel, ivory, and so on. The 

 worn crown forms a slightly convex or concave surface, marked by transverse 

 ridges of different degrees of hardness and height, and thus yields a masticating 

 instrument of the greatest power and efficiency. 



In their food, elephants are strictly herbivorous, subsisting chiefly 

 upon roots, twigs, leaves, and young shoots or trees, or grass and 

 other herbage; such food being conveyed to the mouth by the aid of the flexible 



Habits 



