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 Labradorean 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 
