ELEPHANT AND MASTODON. 95 



third milk molar of the upper jaw in this species is followed 

 by a cori'esponding vertical successor. It is of importance to 

 observe this apparent irregularity in the order of suppression. 

 In Dinotherium the two last premolars are developed, the 

 two anterior being suppressed ; in M. Ohioticus the whole 

 four remain undeveloped ; while in M. angustidens the penul- 

 timate alone is developed, the two anterior and the last 

 being suppressed. A similar order of suppression has been 

 observed in the premolars of M. longirostris. 



In regard to the lower jaw, there is no evidence yet that a 

 premolar is included in the dental succession of the inferior 

 grinders. Yon Meyer, with doubt, assigns this place to a 

 detached tooth which he figures,' but the determination is 

 merely conjectural, Kaup referring it to his M. longirostris ; 

 and it is by no means certain that this specimen does not 

 belong to the upper, rather than to the lower jaw. That a 

 rudimentary lower premolar may have been developed in this 

 species is highly probable ; but we are not warranted, in the 

 absence of direct proof, to hazard any inference respecting 

 organs which are liable to be entirely suppressed, and which, 

 when developed, are so rudimentary in form as not to be of 

 functional importance in this tribe of animals. 



The materials to illustrate the dentition of the adult animal 

 have been found in sufdcient abmidance to leave no room for 

 doubt respectiag the characters and siiccession of the true 

 molars. The antepenultimate, or first,^ is seen in the San- 

 sans specimen from M. Lartet, in situ in the left side of the 

 upper jaw, along with the third milk molar which we have 

 described. It is an oblong tooth, in the condition of an 

 almost unworn germ, having the crown divided into three 

 distinct ridges, with a well-marked basal eingulum on the 

 inside, and a small back talon. It measures 4"13 inches in 

 length by 2*75 of width in front, and 2 '75 behind. 



Another example of this tooth appears to be furnished by 

 fig. 5, of tab. 1, of Von Meyer's memoir. The crown has 

 the same three-ridged form as the Sansans specimen, with 

 which it agrees very closely in dimensions, being 4*2 inches 

 long by 2*7 in width. Yon Meyer refers it with doubt to 

 the third molar of the lower jaw, right side of this species, 

 while Kaup assigns to it the same position in the lower jaw 

 of his M. longirostris.^ 



The penultimate, or second true molar, is shown in situ 

 along with the last, in another instructive Gascon specimen 

 from M. Lartet, displayed in the Paris Museum. This frag- 

 ment, likewise, is of the left side of the upper jaw. Of the 



' Loe. cit. tab. i. fig. 2, ^ De Blainville, OstiJographie, pi. xv. fig. 4. 



' Loc. cit. p. 81. 



