667 



the northeastern (Greenland-Iceland) or northwestern (Behring 

 Strait) routes during the interglacial epochs. Another prominent 

 iVature of the land faunas far from the ice was a group of southern 

 forms consisting of gigantic sloths, armadillos, and water-hogs, 

 whose forebears had come from South America a little earlier, by 

 way of the Isthmus of Panama. 



The boreal group. As in the Pliocene, proboscidians dominated 

 the fields and forests of middle latitudes. The mammoth ranged 



v(j. An interpretation of Mastodon atncrlciinus by G. M. Gleeson. 

 (From painting in National Museum, Washington!) 



from Mexico northward, reaching Canada and Alaska during inter- 

 glacial epochs. In Siberia, the mammoth was covered with wool 

 and hair, and was obviously adapted to a cold climate. The mam- 

 moth survived the glacial period in America, and its tusks and 

 skeletons are found in beds of peat and muck which have accumu- 

 lated since, in northern United States and Canada. The mastodon 

 also ranged northward into Canada, but since it emigrated to South 

 America and crossed the tropics, it must have been adapted to a 



