ROCKY MOUNTAIN FLYING-SQUIRREL 207 
The fur of the throat and belly is a grayish-white, without any tinge of 
buff colour ; tail, blackish-brown above, a little paler beneath. 
DIMENSIONS. 
Prom point of nose to root of tail, 
Tail (vertebras), 
“ (including fur), /- 
Heel to longest middle toe, 
Height of ear posteriorly, 
Breadth between the outer edges of the flying membrane, 
Inches. 
84 
5 
64 
H 
n 
If 
41 
Richardson states that there is a specimen in the Hudson’s Bay 
Museum, which measures nine inches from the point of the nose to the 
root of the tail. 
HABITS. 
We have learned little of the habits of this animal. Drummond, who 
obtained it on the Rocky Mountains, states that it lives in pine forests, 
seldom venturing from its retreats except during the night. 
From its heavy structure, and the shortness of the bony process that 
supports the flying membrane, we are led to infer that it is less capable of 
supporting itself in sailing from one tree to another, than the other species 
of this genus. 
GEOGRAPHICAL DISTRIBUTION. 
Both the specimens of Drummond and Townsend were obtained in 
crossing the Rocky Mountains on the usual route to the Columbia river. 
We have no doubt this species will be found on the western side of the 
Rocky Mountains, from the Russian settlements through Oregon to 
California. 
GENERAL REMARKS. 
Richardson regarded this species as a variety of Pteromys sabrinus (see 
our first volume, p. 134), and adopted for it the name alpinus, not to desig- 
nate a species but a variety. We, on the other hand, consider it a true 
species, and have applied to it the name of P. alpinus, quoting Richard- 
son’s var. alpinus a,s a synonyme. 
On comparing the specimen from which our drawing was made, with P, 
