Arctic Loon (ravia arctica pacifica (see pp. 31, 158). 



4. Old Crow 



nn HE GAP IN OUR INFORMATION about the geographical distribution of 

 ■*■ life in the northern interior of Yukon Territory has been especially 

 significant because there we could expect to find a transition from the 

 specialized fauna of Alaska to the more generalized American fauna 

 of the Mackenzie Valley, representing the central part of the American 

 continent. 



The Terrain 



The Porcupine River extends the Alaskan Yukon Valley eastward 

 across Yukon Territory to within 50 miles of the Mackenzie River 

 and the arctic coast of Canada (see maps, figs. 1 and 7). Passes 

 through the British and Richardson Mountains from Old Crow River 

 Valley to the arctic coast are numerous and shorter and lower than 

 the passes through the Alaskan part of the Brooks Range. Macdougall 

 Pass through the Richardson Mountains, leading from the eastern 

 tributaries of the Porcupine to the Mackenzie watershed, is shorter 

 and, with an elevation of 1,200 feet, lower than any pass through the 



149 



