70 THE CHICAGO ACADEMY OF SCIENCES. 





mn 

QUATERNARY N 
ONS 
NORTH AMERICA 
=~ = ~— miles 


| LEGEND 
OCEANIC BASINS 
MARINE WATERS 

INCLUDING MARINE SEDIMENTS 
a LANDS 
ICE 
MARINE CURRENTS 
POLAR — 
EQUATORIAL ———s= 
N10 

120 

FGs ee 
Map of North America showing maximum development of the ice sheet 
and indicating (1, 2, 3, 4, 5) probable areas in which the life of the englaciated 
territory was preserved during the Ice Age. Willis, Journal of Geology, XVII, 
p. 601. 
ing of the fauna over this immense territory. It must also be borne 
in mind that in the region immediately south of the ice sheet the faunas 
of several types of country were crowded together—arctic, subarctic, 
temperate—and as the ice receded, the mirgation northward was in the 
reverse order of the southward migration, the arctic forms following 
