xl 



INTRODUCTION. 



in Europe, Asia, or Africa. The types of Bradypus and 

 Dasypus were, however, richly represented by diversified 

 and gigantic specific forms in South America, during 

 the geological period immediately preceding the present ; 

 and fossil remains of extinct species of Cama, Ccelogenys, 

 Ctenomys, and Cebus, have hitherto been detected exclu- 

 sively in the continent where these genera still as ex- 

 clusively exist. AucJienia more remotely typifies Macr- 

 auchenia. The murine fossils in the rich collection of 

 remains from Brazilian caverns, lately received at the 

 British Museum, all belong to the genus Hesperomys, the 

 aboriginal living representative of the Murida in South 

 America ; not a single fossil is referable to a true Old 

 World Mus, though numbers of the common Eat and 

 Mouse have been imported into South America since its 

 discovery by Europeans. With regard to the Sloths and 

 Armadillos, they now seem, after the rich harvest of 

 bulky Glyptodons, Mylodons, Pachytheriums, and the 

 more gigantic Megatherioid quadrupeds, to be the last rem- 

 nants of a Mammalian Fauna, which once almost equalled 

 in the size and number of its species that of the Europseo- 

 Asiatic expanse, and was as peculiarly characteristic of 

 the remote continent in which almost all its representa- 

 tives have been entombed. 



In North America the most abundant Mammalian fos- 

 sils of the corresponding recent geological epoch belong to 

 a species of Mastodon (M. giganteus) peculiar to that con- 

 tinent. Since, however, North America borders closely 

 upon Asia at its northern basis, and is connected by its 

 opposite apex with South America, it perfectly accords 

 with the analogies of the geographical relations of the 

 last-extirpated series of Mammals of the Old World that 

 the Asiatic Mammoth and the South American Mega- 



