12 NORTH AMERICAN FAUNA. [no. 19. 



the water's edg-e, and the timber i,s very sparsely sprinkled over them. 

 The rocks found here and a few in Thirty-Mile River are the last we 

 saw showing signs of glaciation. Lake Lcbarge is quite different from 

 Lake Marsh, and is more similar to Lakes Tagish and Bennett, though 

 all the Hudsonian elements of these are not present. 



River subdivision : This area includes the section from the foot of 

 Lake Lebarge to the mouth of the Pell v River at Fort Selkirk. There 

 is very little variety in the character of the country between these 

 points. Thirty -Mile River, which proceeds from Lake Lebarge, is a 

 swift, narrow stream, and at low water is barely navigalile for small 

 steamers. A conspicuous feature of its banks, which are cut abruptly 

 like those of Fiftv-Mile River, is a narrow ribbon-like stratum of vol- 

 canic ash about 6 inches below the surface that may be seen wherever 

 the bank is exposed. On the mountains a short distance from the river 

 the forest of spruce is heavier and purer than an}" previousl}' noted. 

 The poplars and willows are more confined to the brink of the river, 

 and the birches are scattered. Thirt3"-Mile River is simply that por- 

 tion of the Yukon between Lake Lebarge and the mouth of the Hoota- 

 linqua orTeslin River. The stream is greatly augmented b}^ the 

 waters of the Hootalinqua, and from this point on to Fort Selkirk is 

 known as the Lewes River. Below the Hootalinqua it cuts through 

 the Semenow Hills, for the most part abrupt, rock}', and rather barren 

 mountains from 2,000 to 3,000 feet high. Near their bases and at the 

 water's edge are forested areas, but the exposed hillsides are covered 

 with boreal sagebrush {A7'temisiafngida)^ with here and there a pros- 

 trate juniper or a small clump of spruces. The river now widens 

 rapidly, receiving in succession the waters of the Big Salmon, the 

 Little Salmon, and the Nordenskiold. The rolling hills are sometimes 

 a mile or several miles from the river bank, with low willow swamps 

 intervening. Islands varying from 1 to 100 acres in extent and 

 covered with luxuriant vegetation are abundant. The distribution 

 of trees on the small, regular-shaped islands is very uniform, this 

 different kinds being grouped in concentric belts. Alders generally 

 form the outer margin; next come the willows; next the poplars, 

 rising somewhat higher; and finally the dark-green spruces, which 

 occupy the central area. The whole effect is quite picturesque. On 

 the larger islands the spruces are larger, and usually predominate to 

 such an extent that almost everything else should be classed as under- 

 growth (including trees and shrubs belonging to the genera Alnus, 

 Salix, Pojndus^ Lepargyrcm^ Cornus^ Vihurnwn, jRosa, Zedmn, Yac- 

 dnium^ Hihes^ and others). Lodgepole pines still occur, though unlike 

 the spruces they nowhere form continuous forest and disappear entirely 

 a short distance beyond Fort Selkirk. 



The Canadian Yukon district as a whole is very well marked. Char- 

 acteristic mammals are the gray-headed chipmunk {Eutamias caniceps), 



