SUCCESSIVE MAMMALIAN FAUNAS 211 



horses, large and small, the camels and llamas, many species 

 of bisons, some of enormous proportions, several forms allied 

 to the Musk-Ox, the elephants and fmastodons, the fgiant 

 beavers and South American water-hogs, the huge fground- 

 sloths and jglyptodonts, have all disappeared, leaving a con- 

 tinent, that, by contrast, is "zoologically impoverished." 

 The Pleistocene fauna was strangely mixed in character, the 

 free roads of migration bringing together Old World and South 

 American types, and mingling them with indigenous forms 

 in a cosmopolitan assemblage. 



Turning to South America, we find in the pampas of Argen- 

 tina a wonderful museum of Pleistocene mammals, such as 

 occurs nowhere else in the known world, and this is supple- 

 mented by the very rich collections gathered from the caverns 

 of Brazil and from deposits of Ecuador and BoUvia, and thus 

 aU the important regions of the continent, save the far south, 

 are well represented. These faunas are far stranger than the 

 corresponding ones of North America and differ more radically 

 from those of modern times, since they include a much larger 

 proportion of extinct types, and the extinctions have swept 

 away not only species and genera, but families and orders as 

 well. 



The South American Pleistocene assemblage of mammals 

 is very clearly divisible into two elements : (1) the immigrants 

 from the north, which reached the southern continent in suc- 

 cessive waves of migration, that have left records of themselves 

 as early as the older Pliocene, perhaps even the upper Miocene, 

 and (2) the indigenous element, which had a very long history 

 of development in South America. To the immigrant class be- 

 longed all of the Carnivora, which therefore resembled their 

 North American relatives, but were less varied in character. Of 

 the bears, only the huge, fshort-faced kind (\Arctotherium, Fig. 

 275, p. 549) are known, and it is not likely that true bears existed 

 except in the Andes, as is also the case to-day. Of the cat 

 family, the fsabre-tooth tigers {"fSmilodon) were as common in 



