70 NORTH AMERICAN FAUNA. [no. 16. 



(4) The Feather River or (Jidnrij dap^ between Blount Lassen aiul the 

 high ridge northwest of Honey Lake — the northern end of tlie Sierra 

 l)reper. This ga]) is the shallowest, narrowest, most irregular, and 

 least etCeetive of all, and is the only one which has not been cut deeply 

 and coni])letely through the range by a large river. The Boreal zones 

 of the two sides, at the points where they come nearest together, which 

 is southeast of the southeastern extension of the boreal plateau on 

 which Lassen stands, are not sejiarated. a}»parently, by more than 15 

 miles. The distance between the Iludsonian elements appears to be 

 several times greater. This region needs further exploration. 



Fully half of the boreal species of Shasta are common to both the 

 Sierra Nevada and the Cascade IJange, aiul some of them extend over 

 the entire length of the Sierra-Cascade system, inhabiting the princi- 

 pal boreal summits all the way from British Columbia to Mount Whit- 

 ney: others are restricted to particular parts of the mountains, and 

 each of the ibur gaps mentioned forms a barrier beyond which certain 

 species do not pass. Therefore, in contrasting the boreal faunas and 

 floras of Shasta with corresponding faunas and floras of the Sierra 

 Nevada and Cascade llange it is necessary to flx definite limits to the 

 terms employed. The term 'Sierra,' as nsed in the table headings and 

 following (iiscnssion, is restricted to the lofty range extending from 

 Mount Whitney northward a little beyond Honey Lake; the 'Cas- 

 cades,' to the Cascades of Oregon. In other words, the term ' Sieri a ' is 

 restricted so as not to include Shasta or Lassen;' the term 'Cascades' 

 so as not to include the Casca<lcs of Washington. 



The paucity of animal and plant life on Shasta, contrasted with that 

 of the Sierra and Cascades, has been already noted aiul is clearly 

 shown in the following tables. The explanation, briefly stated, is that 

 Shasta, on account of its aridity and relatively small area, is incapable 

 of supporting so rich a fauna and flora as either of the extensive ranges 

 between which it is situated. It is m^t assumed that all of the boreal 

 si)ecies inhabiting Shasta were discovered by us, but in the case of the 

 Canadian and Iludsonian mammals and birds, and the Iludsonian and 

 Alpine plants it is believe<l that the number which escaped detection 

 is too small to nuiterially alter the results here given. ^ 



In grouping the species for study it seems ii'.ost logical to arrange 

 the mammals, birds, and plants in two principal categories: [a) Boreal 



' The flora and fauna of Lassen are not known in sufficient detail to admit of com- 

 plete comiiarisons in cither direction; hence this mountain is omitted from consid- 

 eration in the accompanyinjj tables. At the sauK^ time it should )>e stated that 

 Lassen is clearly a i)art of the Sierra, so far as its fauna is concerned. 



-The accomi)anyiiif^ jierceiitages and lists of species are jirovisional and subject 

 to revision. They aie based on ])resent inioruiaiion and will, of course, be corrected 

 and 8ni)plementcd liy future field work, 'i'liey are suriiciently near the truth, how- 

 ever, to demonstrate certain facts and warrant certain deductions and iieneraliza- 

 tionsof v(^ry j;i<'at interest in connection witii the oriuin of tlie lioie.il lauiias ami 

 floras of the Sierra Nevada and Cascade Range. 



