232 A BOOK-LOVER'S HOLIDAYS 



America by another temporary land bridge, 

 but from another continent, South America. 

 These were the ground-sloths, giant edentates, 

 which reached an extraordinary development 

 in the southern half of our hemisphere, where 

 distant and diminutive relatives — tree-sloths, 

 ant-eaters, armadillos — still live. The most 

 plentiful of these California ground -sloths, the 

 mylodon, was about the size of a rhinoceros; 

 an unwieldy, slow-moving creature, feeding on 

 plants, and in appearance utterly unlike any- 

 thing now living. 



Together with these great beasts belonging 

 to stocks that in recent geologic time had im- 

 migrated hither from the Old World and from 

 the southern half of the New World was an- 

 other huge beast of remote native ancestry. 

 This was a giant camel, with a neck almost like 

 that of a giraffe. Camels — including llamas — 

 developed in North America. Their evolu- 

 tionary history certainly stretched through a 

 period of two or three million — perhaps four 

 or five million — years on this continent, reach- 

 ing back to a little Eocene ancestor no bigger 

 than a jack-rabbit. Yet after living and develop- 

 ing in the land through these untold ages, over 

 a period inconceivably long to our apprehension, 

 the camels completely died out on this continent 



