MAMMALIA. 425 



jaw. They are successively developed, so that an Elephant 

 may have in each jaw not less than six of these enormous 

 molar teeth in the course of its life, or twenty-four in all, 

 although never more than two are seen in each jaw at the 

 same time. As the first tooth wears away, the second tooth 

 is advancing forward; when the first becomes worn and useless 

 the second tooth takes its place, its former position "being now 

 occupied hy the third tooth, which in course of time is carried 

 forward to the front of the mouth, serves its distinct purpose, 

 and when worn down is succeeded hy that which was the 

 fourth. 



"There are few examples of natural structures," says 

 Professor Owen, "that manifest a more striking adaptation of 

 a highly complex and beautiful structure to the exigencies of 

 the animal endowed with it, than the grinding teeth of the 

 Elephant. Thus the jaw is not encumbered with the whole 

 weight of the massive tooth at once, hut it is formed by degrees 

 as it is required; the sub-division of the crown into a number 

 of successive plates, and of the plates into sub -cylindrical pro- 

 cesses, presenting the conditions most favourable to progressive 

 formation."* Another advantage is pointed out by the same 

 high authority: "The tooth in front, which is partially worn 

 down, is fitted for the first coarse grinding of the branches of 

 a tree; the transverse enamelled ridges of the succeeding part 

 of the tooth divide the food (as it passes on towards the 

 throat) into smaller fragments, and the posterior islands and 

 tubercules of enamel pound it to the pulp fit for deglutition." 



It may readily be supposed that the number and thickness 

 of the plates, the shape of the teeth, and the different patterns 

 in which the enamel is arranged, form characters by which the 

 teeth of the same species in different stages of maturity may 

 be recognised, and that they also furnish the means of 

 separating those of the African from the Asiatic Elephant; 

 and both of these from that extinct species known as the 

 Mammoth (Elephas primigenius). 



The teeth of the Mammoth, which are thus easily distin- 

 guishable, are found in the superficial unstratified deposits of 

 the continent of Europe; and with them are associated the 

 remains of two other animals, belonging to the present order, 

 and now found only in warmer latitudes the Hippopotamus 

 and Rhinoceros. 



* On British Fossil Mammalia. 



