MAMMALIA. 



23 



Tlii'ee genera of tlie order are known, tlie still living Elephas^ 

 and the extinct Mastodon and Dinothe7'ium. Some related 

 forms like Dhiocrata abounded in the Eocene. Dinothe7'iu7n is 

 found only in the Miocene and Pliocene of the Old World. The 

 Elephants {Mastodon and Elephas) appear suddenly, without 

 immediate ancestors, as far as discoveries Jiow show. While 

 Dinotlieriuni is a generalized proboscidian, it may not be con- 

 sidei-ed as in the line of descent of the Elephant. The Eocene 

 and Miocene strata of America, Europe and India, are so well 

 known that some other region seems more likelj^ to supply the 

 missing links. 



Mastodon appeared in the Middle Miocene of Eui'ope, and in 

 Lower Pliocene of America. Elephas appeared in both conti- 

 nents somewhat later than Mastodon. Only in America did 

 Mastodon linger through the Quaternary. 



Elephas lyrimigenius (''Mammoth") roamed over all the 

 Arctic regions in the Post-tertiarj^, but the United States and 

 Mexico were occupied by E. Americamis. The latter species is, 

 however, regarded by many authorities as only a modification of 

 the mammoth. Two species of Elephas have been named from 

 South America. 



Three species of DinotTierium. have been named ; some four- 

 teen of Elephas^ and twenty of Mastodon. The last two genera 

 blend together by gradations of structure. 



No. 38. [132J Elephas primigenins, Blnm. 



Lower Jaw, Young (cast). Tliis is 

 the latest form of true Elephant which 

 lived in a temperate latitude; the best 

 known of all the fossil species, and the 

 most highly specialized member of the 

 order. The range of the animal was ap- 

 parently between the 40thand 70th parallels 

 of latitude; and its remains are found ex- 

 clusively in Pleistocene deposits. The in- 

 habitants of Siberia call it Mammoth, or 

 subterranean Mole, believing that it lived 

 under ground. It is not a little singular 

 that Darwin found a theory held by the 

 people of the Pampas that the Mastodon 

 was a burrowing animal. The primeval Elephant greatly exceeded in size 

 the living species. It had broader grinders; narrower, more numerous and 

 close-set transverse plates and ridges; a more parallel position of the right and 

 left sockets of the grinders; a greater length of the tusks; a larger and more 



