THE BOREAL FAUNA AND FLORA OF SHASTA CONTRASTED 

 WITH CORRESPONDING FAUNAS AND FLORAS OF THE SIERRA 

 AND THE CASCADES. 



Ill considering' the relations of the boreal iaiiiias and lioras of Shasta 

 to those of other parts of the Sierra-Cascade system it is necessary at 

 the outset to have a clear conception not only of the extent of the 

 range as a whole, bnt also of the iiuniber and magnitude of the breaks 

 or gaps in the continuity of its boreal fauna and Hora. The Cascade 

 Kange enters the State of Washington from British Columbia in lati- 

 tude 49° and pushes southward completely across AYashington and 

 Oregon; its continuation, the Sierra Nevada, traverses California 

 for a distance of 500 miles, ending a little south of Mount Whitney, in 

 about latitude 3(P. The Cascade-Sierra system, therefore, extends over 

 13 degrees of latitude, and has a total length of fully 1,000 miles. For the 

 whole of this distance it rises abruptly from a low region, whose faunas 

 and floras are in the southern part Sonoran, in the northern i)art Tran- 

 sition. The field work of the Biological Survey has shown that the 

 narrow boreal band which occui»ies the higher parts of the range is not 

 continuous, but is interrupted by four important gaps, through which 

 Transition zone species pass freely in broad belts from one side to the 

 other. These gaps, begining at the north, are: 



■ (1) The Columbia 6'«7>, or gorge of the Columbia lliver, on the bound- 

 ary between Washington and Oregon, where the breadth of the Tran- 

 sition zone seems to be less than ."iO miles. ^ 



(2) The Klamath Gaj), on the boundary between Oregon and Califor- 

 nia, extending from a little south of Mount Pitt in Oregon to Mount 

 Shasta in California, a distance of about 50 miles. This interval is 

 interrui)ted by one or two detached groups of low mountains on the 

 California side, and by long ridges on both sides, whose summits are 

 inhabited by boreal species, materially decreasing the actual breadth 

 of the gap. 



(3) The Pitt River Gap, between Mounts Shasta and Lassen in north- 

 ern California. The breadth of the Transition zone here is about 00 

 miles. 



'Although not bearing on the fauna of Shasta, it is interesting to note, in connec- 

 tion with the effects of the Columbia River Gap, that a number of species charac- 

 teristic of the northern Cascades, in the State of Washington, do not occur in the 

 southern Cascades, in Oregon. Among the mammals the most notable sjiecics of 

 this kind are Arctomys calii/atns, ('olloupcnnophiliis safto-atus, ErotomyH (jaiqteri satu- 

 ratiis. Oreamvos montaniis, Pf'roniijscKs orean, I'lttoriiis irashiru/toni, Zapus irinotatiis. 



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