ELEPHANT AND MASTODON. 63 



This upper premolar, as has been pointed out by Professor Owen, 

 takes the place of the second milk molar ; it therefore represents 

 the penultimate of this series. There is no evidence that the 

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

 corresponding vertical successor. It is of importance to observe 

 this apparent irregularity in the order of suppression. In Dino- 

 therium, the two last premolars are developed, the two anterior 

 being suppressed; in M. Ohioticus the whole four remain unde- 

 veloped ; while in M. angustidens, the penultimate alone is deve- 

 loped, 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 pre- 

 molar is included in the dental succession of the inferior grinders. 

 Von Meyer, with doubt, assigns this place to a detached tooth 

 which he figures (Joe. cit. tab. 1. fig. 2.), 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 pro- 

 bable ; 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 rudimen- 

 tary 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 sufficient abundance to leave no room for 

 doubt respecting the characters and succession of the true molars. 

 The antepenultimate, or first, 1 is seen in the Sansans 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 

 cingulum on the inside, and a small back talon. It measures 

 4.13 inches in length by 2.75 of width in front, and 2.25 behind. 



Another example of this tooth appears to be furnished, by fig. 5, 



1 De Blainville, Osteographie, pi. 15. fig. 4. 



