THE TRANSITION ZONE. 25 



(&) The Arid Transition Faunal Area. 



The western or arid division of the Transition zone comprises the 

 western part of the Dakotas, northern Montana east of the Rocky 

 Mountains, southern Assiniboia, small areas in southern Manitoba 

 and Alberta, the higher parts of the Great Basin and the plateau 

 region generally (except the Boreal Mountains), the eastern base of 

 the Cascade-Sierra system, and local areas still farther west, in Ore- 

 gon and California, where it merges into the humid Pacific Coast 

 division. 



In the western arid Transition area the true sage brush {Artemisia 

 tridentata) is the prevailing type of vegetation, although extensive 

 tracts are covered with noble forests of the yellow or bull pine {Pinus 

 ponderosa) and subspecies.^ The sage hen and sharp-tailed grouse, 

 green-tailed towhee, white-tailed jackrabbit {Lepus campestris), pal- 

 lid voles (subgenus Laguriis), and certain ground squirrels are char- 

 acteristic species. In the northern parts of the Great Basin (northern 

 and eastern Washington, northeastern Oregon, and northwestern 

 Idaho) the large Columbia or Lewis and Clark ground squirrel {Sper- 

 mophilus columhianus) is common in the Transition zone, whence it 

 ranges northward into the Boreal. East of the Rocky Mountains, on 

 the northern plains (in North Dakota, northern Montana, and parts 

 of Assiniboia and Manitoba), it is replaced hy a verj" diiferent spe- 

 cies {8. riclmrdsoni)^ which resembles a small prairie dog {Cynomys) 

 so closely that it is often mistaken for that animal. 



Crops of the Arid Transition Faunal Area. 



[Lists very incomplete.] 

 CEREALS. 



Wlieat. 



Ladoga. 

 Red Fife. 



Saskatchewan Fife (^). 

 Scotch Fife. 





Oats. 



American Banner. 

 Black Tartarian. 

 Lincoln. 



Welcome. 

 White Russian. 



Corn. 



Angel of Midnight (?). Longfellow (,?). 



Canadian Eiglit-Row Yellow Flint (3). Squaw. 



King Philip (.?). Stowell Evergreen (2). 



' Among the distinctive humbler plants which recur throughout the pine belt from 

 Arizona to Oregon two small shrubs, Berberis repens and Ceanothus fendleri, are 

 conspicuous. Gilia aggregata, a small plant with handsome red flowers, is also 

 common in this belt. 



