10 NORTH AMERICAN FAUNA. [wo. 16. 
(4) The Feather River or Quincy Gap, between Mount Lassen and the 
high ridge northwest of Honey Lake—the northern end of the Sierra 
preper. This gap is the shallowest, narrowest, most irregular, and 
least effective of all, and is the only one which has not been cut deeply 
and completely 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 separated, apparently, by more than 15 
miles. The distance between the Hudsonian 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 Range, and 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 four gaps mentioned forms « barrier beyond which certain 
species do not pass. Therefore, in contrasting the boreal faunas aud 
floras of Shasta with corresponding faunas and floras of the Sierra 
Nevada and Cascade Range it is necessary to fix definite limits to the 
terms employed. The term ‘Sierra,’ as used in the table headings and 
following discussion, 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 ‘Sierra’ is 
restricted so as not to include Shasta or Lassen;' the term ‘Cascades’ 
so as not to include the Cascades of Washington. 
The paucity of animal and plant life on Shasta, contrasted with that 
of the Sierra and Cascades, has been already noted and 1s clearly 
shown in the following tables. The explanation, briefly stated, is that 
Shasta, on account of its aridity aud 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 not assumed that all of the boreal 
species inhabiting Shasta were discovered by us, but in the case of the 
Canadian and Hudsonian mammals and birds, and the Hudsonian and 
Alpine plants it is believed that the number which escaped detection 
is too small to materially alter the results here given.’ 
In grouping the species for study it seems most 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 comparisons in either direction; hence this mountain is omitted from consid- 
eration in the accompanying tables. At the same time it should he stated that 
Lassen is clearly a part of the Sierra, so far as its fauna is concerned. 
2The accompanying percentages and lists of species are provisional and subject 
to revision. They are based on present information and will, of course, be corrected 
and supplemented hy future field work. They are sufficiently near the truth, how- 
ever, to demonstrate certain facts and warrant certain deductions and yveneraliza- 
tions of very great interest in connection with the origin of the boreal faunas and 
floras of the Sierra Nevada and Cascade Range. 
