72 NORTH AMERICAN FAT'NA. [n-o.16. 



from the Cascades; 15 are common to Shasta and the Casca<h's but 

 are not known from the Sierra; and 8 are restricted to Shasta. 



Three mammals. 5 birds, and (!S }»hints are believed to be restricted 

 to the Hudsonian and Alpine zones. Of these, 2 mammals, ."> birds, 

 and 30 plants are common to the Sierr.i and the Cascades; one mam- 

 mal, 1 bird, and 18 plants are common to Shasta and the Sierra but 

 are not known from the Cascades; and no mammal, 1 bird, and 12 

 plants are common to Shasta and the Cascades, but are not known 

 from the Sierra. Five Hudsonian- Alpine i)lants from Shasta are not 

 known from cither the Sierra or the Cascades. 



These c<)m]>arisons show: 



(1) That of the boreal species known from Shasta, including those 

 which ranji'e down into the Transition zone, 87 ])ercent of the birds, 

 72 percent of the mammals, and only at) percent of the jdants are 

 common to the Sierra and the Cascades. 



(2) That of the exclusively boreal species known from Shasta, 85 per- 

 cent of the birds, 70 percent of the mammals, and 40 percent of the 

 plants are common to the Sierra and the Cascades. 



(3) That of the exclusively Hudsonian and Alpine species known 

 from Shasta, (50 percent of the birds, 07 percent of the mammals, and 

 44 percent of the plants are common to the Sierra and the Cascades. 



(4) That in each instance, as would be expected, the i»crcenta,i;e of 

 species common to the two ranges is greater in the case of those rang- 

 ing (h)wn into the Transition zone than in those restricted to the Boreal, 

 for the obvious reason that geogra[)hically the Boreal belt is broken by 

 broad gaps, while the Transition zone is practically continuous. 



(5) That of the birds, mammals, and plants of Shasta, birds have by 

 far the largest jjcrcentage of species common to the Sierra and the 

 Cascades, mammals next, and plants least of all. This corresponds 

 with the relative ])owers of dispersion i)ossessed by these grou])s. 



Arranged ])riinarily by groups instead of zone limits, it appears that 

 the percentages of Shastai birds connnon to the Sierra and tiie Cascades 

 are as follows: Of boreal species, in(duding those which range down 

 into the Transition zotie, 87 percent ; of species restricted to the Boreal 

 zones, 85 percent; of species restricted to the Hudsonian and Alpine 

 zones, (10 percent. 



The ))ercentages of Shasta mammals common t<> the Sierra an<l the 

 Cascades are: Of boreal spe(;ies, including those which range down into 

 the Transition zone, 72 percent; of species restricted to the P>oreal 

 zones, 70 I'crcent; of species resti'icted to tiic lludsoniaii and Alpine 

 zones, 07 i)ercent.' 



The percentages ol" Sliasta plants common to the Sierra and the Cas- 

 cades are: Of boreal species, including those which range down into 

 the Transition zone, 40 lu'rcent; of s])ecies restricted to the Boreal 



I 'I'lui iiiiniliii- (if I linls<iiii;ni-Aliiiiiii species is loo siimll Id -ivii this pcvrontngo 

 luuch value . 



