CHAP. VII.] MAMMALIA OF THE NEW WORLD. 141 



to ascertain their relations to each other, and to see how far 

 they elucidate the problem of the birth-place and subsequent 

 migrations of the several families and genera. We have already- 

 pointed out the remarkable features of the Quaternary (or Post- 

 Pliocene) fauna of North America, and now proceed to discuss 

 that of the various Tertiary periods, which is closely connected 

 with the extinct fauna of Europe. 



The Tertiary Mammalia of North America . at present de- 

 scribed belong to from eighty to one hundred genera, while 

 those of Europe are nearly double that number ; yet only 

 eighteen genera are common to the two faunas, and of these 

 eight are living and belong cliiefly to the Pliocene period. 

 Taking first, the genera which in America do not go l)ack beyond 

 the Pliocene period ("ten in number), we iind that eight of them 

 in Europe go back to the Upper Miocene. These are Fdis, 

 Pseudcelurus, Hipparion, Cervus, Mastodon, Ehphas (in India), 

 Castor and Hystrix ; while another, Canis, goes back to the 

 Upper Eocene and the tenth, Equus, confined to the newer 

 Pliocene or perhaps to the Post-Pliocene in America, extends 

 back to the older Pliocene in Europe. Of the seven European 

 genera which are confined to the Miocene period in America, 

 three, Hymnodon, AncMtheriuin, and LopModon go back to the 

 Eocene in Europe; three others, Machairodus, Bhinoceros, and 

 Aceratherium, are also of Miocene age in Europe; Ampliicyon goes 

 back to the Lower jNliocene of Europe, Lopliiotlurmm belongs 

 to the Eocene of both countries. 



If we turn now to families instead of genera, we find that the 

 same general rule prevails. Mustelidas (weasels), Ursida? (bears), 

 true Equidee (liorses), and Bovidre (oxen &c.), go no further back 

 in America than the Pliocene, while they all go back to the 

 Miocene in Europe. Suidae (swine) and Anoplotheridee (extinct) 

 are found in the American Miocene and in the European Eocene. 

 Anchitheridffi (extinct) reach the Upper Eocene in America, 

 while in Europe they range through Upper, Middle, and Lower 

 Eocene. Cervidse (deer) alone are Miocene in both countries. 

 There remain two families in wdiich America has the pre- 

 eminence. CamelidaB (camels) were wonderfully developed in 



