148 BRITISH AND EUROPEAN FOSSIL ELEPHANTS. 



E. (Euelephas) antiquus from the Mammoth corresponds with 

 that of E. (Loxodon) Africanus from E. (Loxodon) meridionalis, 

 the former in each case being Stenocoronine, the latter 

 Eurycoronine. 



Another circumstance that requires to be considered is the 

 manner in which the plane of detrition modifies both the 

 pattern and the antero-posterior diameter of the worn discs 

 at different elevations. In the Mastodons, M. (Trilophodon) 

 Ohioticus 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 consider- 

 able angle with the vertical plane of the ridges. In the 

 Indian 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 rec- 

 tangular, 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 

 circle. 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°. From this 

 circumstance it follows that, as the ivory-cores of the ridges, 

 however compressed, are wedge-shaped bodies, the discs of 

 wear not only necessarily become wider as they get lower, 

 but, from the obliquity of the plane that intercepts the 

 ridges, they expose, in old teeth that are used down to 

 the base, a broader surface than the actual width to the 

 ridges, measured in a straight line. From not paying due 

 regard to the cause, observers have been led to regard what 

 is in reality only an accident of advanced wear in such cases as 

 indicating ' thick-plated ' varieties, and as subversive of the 

 specific distinction between the Mammoth and E. meridionalis. 



2. Indian Elephant. — The leading features of the dentition 

 of this species are so well known from the excellent descrip- 

 tions and figures of Corse, followed up by Cuvier, De Blain- 

 ville, and other comparative anatomists, and the materials 

 are so abundant in European collections, that I shall confine 

 my remarks on the present occasion chiefly to the points 

 which affect the determination of the ridge-formula in the 

 successive teeth. But it is necessary to enter with some 

 detail of evidence upon this part of the subject, as the results 

 to which I have been led differ hi some important respects 



