HISTORY OF THE GREAT LAKES 55 



other does not. We may suppose that the species inhabit- 

 ing the Mississippi during the period preceding the Ice Age 

 were not precluded from advancing up stream towards the 

 highlands of Labrador. But only the hardiest forms, those 

 that could adapt themselves to waters probably brackish and 

 laden with mud, might have succeeded in surviving, though 

 not without becoming stunted in form and undergoing 

 various other changes. Such forms as the pearl-mussel 

 (Margaritana margaritifera), accustomed to pure mountain 

 streams, only survived in isolated localities in the eastern and 

 western parts of its range, becoming extinct in the central 

 parts, where the conditions must have been less favourable for 

 its survival. 



Let us now examine the land fauna of another part of 

 this north-eastern Archaean land surface which is supposed 

 by Professors Upham and Grabau to have stood at a rela- 

 tively much higher level to the lake region than it does at 

 present. Labrador has been amply dealt with, but New- 

 foundland, which must have been completely isolated from 

 the mainland for some time past, being a large island situated 

 at the mouth of the mighty St. Lawrence River, ought 

 to contain some interesting pre-Glacial relicts. We have no 

 reason to assume that Newfoundland has been connected 

 with the mainland since the passing away of the Ice Age, 

 nor is there any evidence to show that mammals or other 

 terrestrial vertebrates have reached the island by swimming 

 across the Strait of Belleisle or down the St. Lawrence,. 

 Geologists tell us that Newfoundland was not overridden 

 by the huge Labrador ean glacier, but that it had a system 

 of local glaciers quite independent of those of the mainland. 

 Even if all the higher parts of the island had been buried 

 in snow and ice, tracts of land near the coast must have 

 remained free from ice, as in Greenland, and so have given 

 shelter to the survivors from pre-Glacial times. This view 

 is certainly strengthened by the fact that all the mammals 

 hitherto observed on the island belong to well-marked varieties 

 or species peculiar to it. The Newfoundland caribou, the 

 only deer inhabiting the island, has antlers differing con- 

 spicuously from those of other races of reindeer, and many 

 authorities now recognise it as a distinct species under the 



