86 NORTH AMERICAX FAUNA. [no. 16. 



one category, and the Sierra species (those south of Klamath (lai)) in 

 another, some additional facts are brought out which emphasize the 

 v.idely ditfeient sources of origin of the distinctively Cascade species 

 on the one hand, and the di.stinctively Sierra species on the other. 

 Of the distinctively Cascade species, 2o ])ercent are derived from 

 mountains farther north, 12 percent are local types, 12 percent belong 

 to transcontinental boreal types, and 25 percent to northwest-coast 

 types. Of the distinctively Sierra species, 50 percent are specially 

 developed local types, and 50 percent belong to types common to the 

 Sierra and the southern IJocky lAfountains. 



These facts point not only to the great antiquity and effectiveness of 

 the Klamath Gap, but also to a former east and west continuity of 

 range of Boreal species between the Eocky Mountains of Utah and 

 Coloiado and the Sierra Nevada of California, a distance of at least 

 500 miles. 



