RODENTIA-SCIURINAE—PTEROM VS ALPINUS. 
289 
List of specimens. 
Catalogue 
number. 
Locality.. 
Whence obtained. 
Nature of 
specimen. 
Nose to— 
Tail to end of— 
Length of 
hind ft. 
Height of 
ear. 
Occip. 
Tail. 
Verteb. 
Hairs. 
193 
2033 
2369 
2370 
2823 
Pembina, Minn...... 
Halifax, N. S. 
C. Cavileer........ 
Dr. J. B. Gilpin... 
......do..... 
Skin...... 
_do.__ 
1. 50 
9.00 
7. 00 
6. 00 
5. 60 
1.60 
1.50 
.65 
.....do.....^ 
Sfcp.nhftrij Me _ _ _ _ 
.T. D. Parker _ _ j 
PTEROMYS ALPINUS. 
Rocky Mountain Flying Squirrel. 
Pteromys sabrinus, var. 0 alpinus , Richardson, Zool. Jour. Ill, April 1828, 519 .—Ib. Fauna Bor. Amer. I, 1829, 
195; plate xviii. 
Pteromys alpinus, Wagner, Suppl. Schreb. Ill, 1843, 230. 
A cd. & Baoh. N. Am. Quad. Ill, 1853, 206 ; plate cxliii, fig. 2. 
Sp. Ch. —Larger than P. sabrinus. Flying membrane with a straight border. Tail longer than the body, exclusive of 
head. (Tail differently colored from the back, and darker?) 
There is a flying squirrel in the museum of the Philadelphia Academy of Natural Sciences, 
labelled “ Pteromys alpinus , Columbia river, Dr. Townsend,” but I am unable to say whether 
it is really the type of Bachman’s description or not. The locality is probably the Rocky 
mountains, as described by Bachman, nearly all of Townsend’s specimens having been labelled 
Columbia river, whether collected there or on the overland march from St. Louis. It is the 
largest I have seen, the flying membrane with only a slight angle at the wrist; the tail very 
broad and full. The colors above are of a yellowish brown, much as in P. oregonensis; the 
tail similarly colored, although described as darker, and but little paler beneath. The under 
fur is dull whitish ; the hairs lead colored at the base. 
The characteristics of the Pteromys alpinus of Audubon and Bachman consist in the larger 
size, the tail longer than the body, (exclusive of the head,) and the straight border of the 
membrane. They also speak of a shorter process on the wrist for the support of the membrane; 
this process, however, in the Academy’s specimen, measures nine-tenths of an inch, or consider¬ 
ably more than in the P. hudsonius. The blackish brown tail, referred to as distinct in color from 
the back, I cannot find, the surfaces of both being very similar. The skin measures 8^ inches 
to root of tail; the tail is broken. 
Richardson at first believed in the existence of the species distinguished as above, and, in fact, 
described a variety alpinus , of P. sabrinus. The receipt of additional specimens, however, 
threw some doubt on the subject in his mind. I have not sufficient data before me to come to 
any very definite conclusion as to there being two species. I cannot find any characteristic 
difference in the shape of the membrane in the specimen here described and P. hudsonius , while 
the latter exhibits much the most of a want of uniformity in color of tail and body of the two. 
37 L 
