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University of California Publications in Zoology [ VoL - 16 



a distinct habitat. Near Nine-mile, on the Walla Walla River, the 

 valley is definitely semi-desert, and sagebrush extends up the side 

 canons, but the vegetation of the higher land is dominated by bunch- 

 grass. Bunchgrass is also dominant on the upper parts of the range 

 of hills south of the Walla Walla River. Yellow pines invade the 

 prairie from the Blue Mountains, coming down along the north and 

 northeastern hillsides and appearing in the bottoms of the canons in 

 the foothills. 



Along Snake River the region is drier than at Prescott and the 

 rocks lie closer to the surface. Along the canons in that region there 

 are high basaltic bluffs and many rocky slopes. Toward the Blue 

 Mountains also there are numerous outcroppings of rocks, but over 

 most of the prairie area rocks are rarely found at the surface of the 

 ground. 



Streams are not numerous in the prairie area. There is a growth 

 of willows and other deciduous trees and shrubs along the smaller 

 streams, but along Snake River there are few native trees or shrubs, 

 so that no cottonwood-willow habitat is formed along this stream. 



CHARACTERISTIC SPECIES OF THE PRAIRIE FAUNA 



Aneides iecanus. 

 Hyla regilla. 

 Chrysemys bellii. 

 Actitis macularius. 

 Numenius americanus. 

 Accipiter velox. 

 Buteo swainsoni. 

 Bubo virginianus occidentalis. 

 Dryobates pubescens homorus. 

 Asyndesmus lewisi. 

 Archilochus alexandri. 

 Selasphorus rufus. 

 Myiochanes richardsoni richard- 

 soni. 



Empidonax trailli trailli. 

 Ammodramus savannarum bimacu- 



latus. 



Biparia riparia. 

 Stelgidopteryx serripennis. 

 Vireosylva gilva swainsoni. 

 Geothlypis trichas occidentalis. 

 Setophaga ruticilla. 

 Troglodytes aedon parkmani. 

 Scapanus orarius schefferi. 

 Mustela arizonensis. 

 Microtus nanus canescens. 

 Perognathus lordi lordi. 



The majority of species known from the Columbia Basin prairie 

 area are known also from the sagebrush area or from the Blue Moun- 

 tains. Of the species here given as unique most will probably later be 

 found to occur in the adjacent faunas. 



