ELEPHANT AND MASTODON. D9 



in the milk molars ; 2 iu the premolars ; and ^ j "^ in 



the true molars. Omitting the consideration of the two 

 anterior milk molars, which are only conjecturally fixed, and 

 of the premolar, the ridge formula furnished by the four last 

 teeth is exactly similar to that of If. Ohioticus— viz., 3 in the 

 last milk molar, and 3 + 3 + 4 in the true molars. 



We have deemed it necessary to go so much into detail on 

 this point, as the definition of the ridge formula constitutes 

 the basis upon which the species of Mastodon are arranged 

 in this work ; and the position could not have been considered 

 as established tiU the exception presented by the teeth of M. 

 angustidens, as ordinarily described, was explained. 



M. Andium. — This species, as defined by De Blainville, 

 includes the teeth, upon which Cuvier founded his ' Masto- 

 donte des Cordilieres ' and ' Mastodonte Humholdien,' besides 

 some South American specimens which the great anatomist 

 erroneously identified with the European M. angustidens. It 

 is closely allied to the latter species, and there are fortunately 

 sufiicient materials available to establish the succession and 

 character of the principal teeth. We shall first describe the 

 grinders of the lower jaw, of which the specimens are most 

 complete. 



Among the fine collection of remains of this species from 

 Buenos Ayres, lately acquired by purchase for the British 

 Museum, there is a beautiful specimen of the left half of the 

 lower jaw, broken only at the symphysis and coronoid process, 

 of a young M. Andium, corresponding in relative size, and in 

 the development of the teeth, with a sucking Indian elephant 

 of about two years old. (See Plate YIII. fig. 1, coj^ied from 

 Plate XL. fig. 13, F.A.S.) It contains the second and third 

 milk molars in situ (the first being broken ofi"), together with 

 the emj)ty alveolar cavity, in which the pulp nucleus of the un- 

 developed first true molar was lodged. The second milk grinder 

 is fully protruded, but had barely come into use, the two front 

 ridges being but slightly abraded ; the third is in the state of 

 an intact germ, and, although fully formed, had not penetrated 

 the gum when the animal died. These teeth are both three- 

 ridged, with a subordinate crest in ft-ont and a small bituber- 

 cular talon behind. They are exactly alike in form, narrow 

 in front but broader backwards. The ridges, as in M. angus- 

 tidens, consist of two pairs of principal points, which, instead 

 of being nearly simple, as in the latter species, are subdivided 

 into a vast number of superficial warty tubercles, which jut 

 into the valleys, forming a bridge or connection between the 

 contiguous ridges, and interrupting the transverse continuity 

 of the valleys. In this respect they bear a greater analogy 



H 2 



