ELEPHANT AND MASTODOX. 101 



in length, 2'85 inelies of width in front, and 3 inches behind. 

 The posterior tooth, which is the last or third true molar, has 

 the crown composed of four principal ridges, and a convex 

 subtriangular heel of several points. The three anterior 

 ridges are partly worn, and finely exhibit the characteristic 

 complex trefoil discs of wear; the two posterior are intact, 

 and the sinuous hollows between them show the very con- 

 siderable layer of cement, which, as previously noticed, is 

 present in a greater quantity in this than in any other species 

 of true mastodon. The dimensions of this tooth are about 

 8 inches in length by 3 '5 inches of width in front, whence it 

 narrows gradually towards the posterior end. Another de- 

 tached specimen in this collection exhibits the same form, 

 and is very nearly of the same size. 



These three specimens, each presenting two molars m sitv,, 

 and respectively derived from the very young, the adolescent, 

 and the aged animal, furnish the clearest demonstration 

 regarding the dentition of the lower jaw in M. Andium. 

 Additional confirmation is dj^rived from the fine specimen 

 of the lower jaw, containing two entire three-ridged teeth 

 m situ, described by M. Laurillard, in M. d'Orbigny's work 

 on South America;' and by Gay's specimen from Chili, figured 

 by De Blainville, which consists of the greater part of an 

 adult lower jaw, with the second and third true molars in 

 situ, these teeth corresjionding in form and dimensions with 

 the penultimate and last molars of the adult lower jaw in the 

 British Museum. The specimen figured by Cuvier^ appears 

 to be the last molar of the lower jaw. 



The materials illustrative of the molar series of the upper 

 jaw in M. Andium are less complete ; but the uniform cor- 

 respondence between the four last teeth in the tipper and 

 lower jaws of M. Ohioticus and M. angustidens would, d priori, 

 lead to the inference that a similar agreement had held in 

 M. Andium. We are not aware of the existence of specimens 

 or figures of the first and second upper milk molars of this 

 species ; but we are warranted in inferring that the second 

 was three-ridged, as in the lower jaw. The third deciduous 

 molar is well represented by Cuvier (tab. ii. fig. 5). The 

 original, brought by Humboldt from Chili, is the specimen 

 upon which the illustrious anatomist founded his M. Hum- 

 boldtii. It is an oblong and nearly rectangular tooth, pre- 

 senting the same square proportions as in M. Ohiotictvs, and 

 having the crown divided into three ridges, which are far 

 advanced in wear, and without either a front or a back talon. 



' Alcide d'Orbigny, Voyage en Sud | and 2. 

 merique. Palseontologie, pi. x. figs. 1 | ^ Qgg_ ]7Qgg_ ^j^]-,_ j;i_ gg_ 4_ 



