632 UNGULATES. 



of dentine with its wavy border of enamel is exposed ; finally the 

 transverse plates themselves are abraded to their common base of 

 dentine, and a smooth and polished tract of that substance is 

 produced. (1) From this basis the roots of the molar are developed, 

 and increase in length, to keep the worn crown on the grinding 

 level, until the reproductive force is exhausted. When the whole 

 extent of a grinder has thus successively come into play, its last 

 part is reduced to a long fang supporting a smooth and polished 

 field of dentine, with sometimes a few remnants of the bottom of the 

 enamel folds at its hinder part, as shown in PL 148, fig. 8. When the 

 complex molar has been reduced to an uniform surface it becomes use- 

 less as an instrument for grinding the coarse vegetable substances on 

 which the Elephant subsists : it is then attacked by the absorbent ac- 

 tion, by which and the pressure of the succeeding tooth it is finally shed. 



The grinding teeth of the Elephant progressively increase in 

 size, and in the number of lamellar divisions, from the first to the 

 last ; and, as the rate of increase in both respects is nearly identical 

 in both jaws, I shall describe them chiefly as they appear in the 

 lower one. 



The first molar which cuts the gum in the course of the second 

 week after birth, has a sub-compressed crown, nine lines in antero- 

 posterior diameter, divided by three transverse clefts into four plates, 

 the third being the broadest and the tooth here measuring six lines 

 across (2) : the first and second plates have two mammilloid summits ; 

 the third and fourth have three or four such ; there is a single, and 

 sometimes a double mammilloid summit, at the fore and back part 

 of the crown : the base slightly contracts, and forms a neck as long 

 as the enamelled crown, but of less breadth, and this divides into 

 an anterior and posterior, long, sub-cylindrical, diverging, but 

 nmtually incurved fangs : the total length of this tooth is one inch 

 and a half. The corresponding upper molar (PI. 148, fig. 1 & 2), 



(1) In the fossil specimen, figured in PI. 147, the left molar fig. 2, I, exhibits all the above 

 described gradations of use ; but the right molar r, through some accident to the opposing 

 tooth in the lower jaw, has not been so worn, but projects beyond the level of the left molar, 

 with the mammiUated margins of the plates entire. 



(2) These are also the dimensions of the first lower molar figured by Mr. Corse, loc. cit,, 

 PI. VI, fig. 1, D, and fig. 3 ; but I have seen the first lower molar of smaller dimensions. 



