16 NOETH AMERICAN FAUNA. [no. 25 



bers of the Biological Survey. The photographs (except the one of 

 the lynx, on Plate XXII, which was contributed by J. W. Mills) 

 were taken by members of the Biological Survey — some by Merritt 

 Cary, the greater number by myself. 



PHYSICAL GEOGRAPHY AND CLIMATOLOGY OF THE MACKENZIE 



BASIN. 



The Mackenzie Basin is here to be understood, in a broad sense, 

 as comprising the area drained by the Mackenzie and its tributaries, 

 and in addition a large section to the north and northeastward of 

 Great Slave and Great Bear lakes, drained by the Coppermine and 

 other smaller rivers tributary to the Arctic Ocean. Thus con- 

 sidered, it comprises a vast region in the northern part of North 

 America, with an area of nearly 700,000 square miles, bounded roughly 

 as follows : On the north by the Arctic Ocean ; on the east by the 

 valleys of the Great Fish, Thelon, Telzoa, and Churchill rivers; on 

 the south by the Churchill and Saskatchewan valleys; and on the west 

 by the main range of the Rocky Mountains. (See Frontispiece.) 



The principal lakes of this region form a more or less connected 

 system, which is a part of a series extending from Lake Superior to 

 the Arctic Sea. These lakes lie along the junction of the primitive or 

 granitic and the newer limestone formations, usually heading in the 

 primitive belt and outletting in the limestone district. They are of 

 irregular shape, usually sending long arms eastward into the primi- 

 tive formation and north and south along the junction of the two 

 systems, though in some cases the southern arms have been filler _, 

 the sediment-bearing streams which enter them. In addition to the 

 large lakes thousands of smaller ones are scattered over the entire 

 region. 



With the exception of a large area at the north, mainly outside 

 the actual drainage basin of the Mackenzie, this region for the most 

 part is covered with woods — the great transcontinental coniferous 

 forest.* The principal trees of this forest are the white and black 

 spruces, whose ranges are coextensive with its limits, and the canoe 

 lurch, tamarack, aspen and balsam poplars, Banksian pine, and 

 balsam fir, which are common in the southern part of the belt, and 

 which terminate, counting from the north, in about the order given. 

 With these are associated, generally in the form of undergrowth, a va- 

 riety of shrubs, some of which, also, have a continuous distribution 

 through the forest zone, while others are more or less restricted in 

 range. 



For convenience of reference this great region may be divided into 

 several areas: The Athabaska Valley; the basin of Athabaska Lake; 



" Sec list of trees ami shrubs, p. 515, for detailed limits of range of the several 



species. 



