The tusks of the extinct Elephas primi genius, or Mammoth, have a bolder and more extensive curvature than those of the Elephas indicus : some have been found which describe a circle ; but, the curve being oblique, they thus clear the head, and point outwards, downwards, and backwards. The numerous fossil tusks of the Mammoth which have been discovered and recorded-, may be ranged under two averages of size: the larger ones at nine feet and a half, the smaller at five feet and a half in length. I have elsewhere* as signed reasons for the probability of the latter belonging to the female Mammoth, which must accordingly have differed from the exist ing elephant of India, and more resembles that of Africa in the development of her tusks ; yet manifesting an intermediate cha racter by their smaller size. Of the tusks which are referable to the male Mammoth, one from the newer tertiary deposits in Essex, measured nine feet ten inches along the outer curve, and two feet five inches in circum ference at its thickest part ; another from Eschscholtz Bay was nine feet two inches in length, and two feet one and a half inches in circumference, and weighed one hundred and sixty pounds. A Mammoth's tusk has been dredged up off Dungeness which measured eleven feet in length. In several of the in stances of Mammoth's tusks from British strata, the ivory has been so little altered as to be fit for the purposes of manufacture ; and the tusks of the Mammoth, which are still better preserved in the frozen drift of Siberia, have long been collected in great numbers as articles of commerce:1 Cuvier states that the elephant of Africa, at least in certain localities, has large tusks in both sexes, and that the female of this species, which lived seventeen years in the menagerie of Louis XIV., had larger tusks than those in any Indian elephant, male or female, of the same size which he had seen. The ivory of the tusks of the African ele phant is most esteemed by the manufacturer for its density and whiteness.
The molar teeth of the elephant are re markable for their great size, even in relation to the bulk of the animal, and for the extreme complexity of their structure. The crown, of which a great proportion is buried in the socket, and very little more than the grinding surface appears above the gum, is deeply di vided into a number of transverse perpen dicular plates (fig. 557), consisting each of a body of dentine (d), coated by a layer of enamel (e), and this again by the less dense bone-like substance (a) which fills the interspaces of the enamelled plates, and here more especially merits the name of " cement," since it binds together the several divisions of the crown before they are fully formed and united by the confluence of their bases into a common body of dentine. As the calcification of each plate begins at the summit, they remain de tached from each other and like so many se parate teeth or denticules, until their base is completed, when it becomes blended with the bases of contiguous plates to form the common body of the crown of the complex tooth from which the roots are next developed.
The plates of the molar teeth of the Si berian Mammoth (Elephas primigenias) are thinner in proportion to their breadth, and are generally a little expanded at the middle ; and they are more numerous in proportion to the size of the crown than in the existing species of Asiatic Elephant. In the African Elephant, on the other hand, the lamellar divisions of the crown are fewer and thicker, and they expand more uniformly from the margins to the centre, yielding a lozenge-form when cut or worn transversely, as in masti cation.
The horizontal as well as vertical course of development of the elephant's grinder is well illustrated by the Mammoth's molar, the last of the lower jaw. The separate digital processes of the posterior plates are still distinct, and adhere only by the re maining cement ; a little in advance we see them united to form the transverse plate ; and, at the opposite extremity of the tooth, the common base of dentine is exposed by which the plates are finally blended into one individual complex grinder*; this never takes place simultaneously along the whole course of the tooth in the larger molars of the existing Indian elephant, or its extinct congener, the Mammoth. The African ele phant, and some of the extinct Indian species, as the El. planifrons, manifest their affinity to the Mastodon by the basal confluence of the hindmost plates before the foremost ones are worn out. The formation of each grinder begins with the summits of the anterior plate, and the rest are completed in succession ; the tooth is gradually advanced in position as its growth proceeds; and, in the existing Indian elephant, the anterior plates are brought into use before the posterior ones are formed. When the complex molar cuts the gum the cement is first rubbed off the digital summits: then their enamel cap is worn away, and the central dentine comes into play with a promi nent enamel ring ; the digital processes are next ground down to their common uniting base, and a transverse tract 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 pro duced.* 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 successively come into play, its last part is reduced to a long fang supporting a smooth and polished field of dentine, with, perhaps, a few remnants of the bottom of the enamel folds at its hinder part. When the complex molar has been thus worn down to a uni form surface it becomes useless as an instru ment for grinding the coarse vegetable sub stances on which the elephant subsists ; it is attacked by the absorbent action, and the wasted portion of the molar is finally shed.