314 i'roceedijSgs op the geological society. 



moulded, and by the confluence of the disks of the separate digita- 

 tions, according to the stage of wear of the teeth. 



The presence or absence of the crimping is very constant in the 

 different species, and very significant as a distinctive mark. Of all 

 the species, fossil and recent, it is most marked in the existing In- 

 dian Elephant, in which the crowns of the molars are comparatively 

 narrow ; and ordinarily it is entirely wanting in E. priinigenius, in 

 which they are broad. The former belongs to the Stenocoronine 

 type of Euele])lias, the latter to the Eurycoronine type. The effect 

 which is brought about in the Mastodons by the crowding of the 

 mammillae so as to present alternate and outlying tubercles, and in 

 the African Elephant by the mesial rhomboidal expansion, is in the 

 Indian Elephant accomplished by the numerous small plicatures of 

 the enamel plates. If these were unfolded, and the plates drawn 

 out to the extent thus gained, the molars of the Indian species would 

 be fully as broad, if not broader than in the Mammoth. Both species, 

 although differing so importantly in these two characters of crimping 

 and breadth of crown, agree in one respect — that, although presenting 

 more or less of secondary flexures, the disks of wear are of nearly 

 uniform width across : neither of them, as a general rule, exhibits 

 any tendency to a mesial loop or to angular expansion ; whereas in 

 E. (Euelephas) antiquus, which has hitherto been so generally con- 

 founded with the Mammoth, the molars present the threefold diff'er- 

 ence of narrow crowns, with crimped enamel, and a certain amoimt 

 of mesial rhomboidal expansion of the disks of wear. This species, 

 in fact, represents among the Eiieleplicmtes Avhat the existing African 

 Elephant does among the Loxodons. The difference of ^. {Euelephas) 

 antiquus from the Mammoth corresponds with that of E. (Loxodon) 

 Africanus from E. (Loxodon) merklionalis, the former in each case 

 being Stenocoronine, the latter Eurycoronine. 



Another circumstance that requires to be considered is the man- 

 ner in which the plane of detrition modifies both the pattern and the 

 antero-posterior diameter of the worn disks at different elevations. 

 In the Mastodons, M. (TrilopJiodon) OMoticus for example, the 

 crowns are rectangular, with only a slight difference of height from 

 front to back; the ridges come successively into wear, but the plane 

 of detrition is nearly level in the same direction, and it makes no 

 considerable angle with the vertical plane of the ridges. In the In- 

 dian Elephant, in consequence of the large increase in the number of 

 ridges, the form of the crown is necessarily modified greatly. The 

 upper molars, instead of being rectangular, are of a subtriangular 

 and rhomboidal form, very high in front, and falling off behind. 

 The anterior ridges attain in the last upper molar a height of 8 inches. 

 In the progress of wear, the tooth moves forward in the arc of a cir- 

 cle. The anterior ridges of the opposed teeth are inclined in front, 

 and, by their triturating action against each other, they are worn away 

 obliquely, and the front part of the crown is ground down to the 

 base before the posterior ridges come into use. The plane of abrasion 

 intercepts the vertical plane of the ridges at an angle of about 60°. 

 Erom this circumstance it follows that, as the ivory cores of the 



