384 P. S. MARTIN 



the fossil distribution of Ovibos (see map of Kitts, 1953) fits the Full- 

 glacial tundra zone fairly well. The barren ground caribou, Rangifer 

 arcticus, is reported from late Pleistocene deposits and its Full- 

 glacial range should be roughly similar to that of Ovibos. Apparently 

 the Postglacial distribution of these species has been so modified by 

 both prehistoric and modern man that their value as tundra indi- 

 cators is uncertain. 



Rather than in eastern North America, the main Full-glacial 

 refugia for tundra mammals and birds (Rand, 1948) lay in ungla- 

 ciated Alaska. The tundra lemmings, Dicrostonyx and Lemmus, have 

 not been found as fossils south of the ice sheet. The present range of 

 the Peary Caribou, Rangifer ardicus pearyi, in northern Greenland 

 and Ellesmere Land dramatizes the ability of caribou to survive at 

 high latitudes under existing glacial conditions. It is barely possible 

 that cyclonic nourishment of the Laurentian ice sheet in central 

 Canada was accompanied by very low precipitation and sufficient 

 ablation to expose the northern part of Greenland and the Arctic 

 Islands. Mercer (1956) indicates ice of uncertain depth, but evidently 

 not very thick, on Baffin Island in the glacial period. The evidence 

 that Banks Island was largely unglaciated (Manning, 1956) adds 

 support to the concept of local, restricted glacial activity in the 

 Arctic during the Full-glacial of the Wisconsin, and of earlier periods. 



The poverty of mammalian biotypes in the tundra of north- 

 eastern Canada compared with northwestern Canada and Alaska is 

 noteworthy. Tundra species of the northwest include Sorex timdren- 

 sis, Citellus undulatus parryi, Clethrionomys ruHlus, Microtus 

 oeconomicus, and M. micrus. These lack vicariants in eastern Canada. 

 A faunal parallel to Hulten's Beringia rejiigium for the Arctic flora 

 seems obvious. 



Late-Glacial (Fig. 3) 



It is sobering to recall that pollen evidence of a North American 

 tundra dates back no farther than Deevey's study of Aroostook 

 County in northern Aiaine (1951). Since then, Livingstone and 

 Livingstone (1958) have confirmed Deevey's tentative recognition 

 of an Allerod type sequence and, by a radiocarbon date of basal 

 organic material, have shown that it was indeed contemporaneous 

 with the Lower Dryas-Allerod-Upper Dryas period in Europe. The 

 subsequent history of Late-glacial tundra, presumably moving 



