16 BRITISH AND EUROPEAN FOSSIL MASTODONS. 



Mastodon, the formula being, Incis. -^ 5 ^an. -^ ; Premol. 



— ; Mol. -3 =11. It exceeds the rest of the species by 8 



molars in both jaws, as M. (Triloph.) angustidens exceeds 

 M. (Triloph.) Ohioticus. A longitudinal belt of enamel has 

 not yet been observed on the tusk of any Elephant. The 

 molars are presented under two forms : in the subgenus 

 Stegodon as ' Dentes complicate' resembling those of Masto- 

 don in the folded form of their crown-eminences, and as 

 ' Dentes lamellosi ' in Loxodon and Euelephas. The con- 

 vexity of the crown- ridges, and the absence of the longi- 

 tudinal, mesial, bipartient cleft, so characteristic of the true 

 Mastodons, are very constant in the Elephants, the only 

 exception, limited to the latter character, being indistinctly 

 seen in an E. (Stegod.) Cliftii. The passage from the Ste- 

 godons into the Loxodons is effected through E. (Steg.) in- 

 signis and E. (Loxod.) planifrons, and from the Loxodons 

 into Euelephas through E. (Lox.) meridionalis and E. (Euel.) 

 Eysudriciis. The anisomerous ridge-formula in Euelephas is 

 not numerically the same in all the species, being in some 

 higher, in others lower ; but they all agree in exhibiting 

 progressive increments. The amount of undulation pre- 

 sented by the worn edges of the enamel plates furnishes a 

 good means of distinguishing the nearly allied fossil species 

 in Euelephas. 



The distinctive and specific characters of Mastodon and 

 Elephant. — A safe criterion by which to test the soundness of 

 any proposed arrangement in Natural History is, that the 

 technical characters, however abiidged, should be ex- 

 ponents, so to speak, of the natural and serial affinities, and 

 in nowise at variance with them. If this test be applied to 

 the ridge formula, as a consistent basis for the arrangement 

 of the Mastodons and Elephants, it will, we believe, not be 

 found wanting : thus the Mastodons ranged under Trilo- 

 phodon and Tetralophodon include all the Elephanto'id species 

 which have the crowns of the molars comparatively simple 

 and uniformly divided into two subequal divisions by a longi- 

 tudinal line or cleft ; the ridges limited in number, each with 

 fewer mam miliary eminences, and invariably more or less 

 concave across ; the enamel thick, and in conical or com- 

 pressed points ; and the valleys between the ridges deep and 

 empty, or with but a sparing quantity of cement. The 

 Elephants, on the other hand, as restricted by the ridge- 

 formula and ranged under Stegodon, Loxodon, and Euelephas, 

 include all the Proboscidean species which have the crowns 

 of the molars more complex, and usually wanting in a longi- 



