290 
U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
PTEROMYS OREGONENSIS, Bach. 
Columbia River Flying Squirrel. 
Pteromys orcgonensis, Bachmajj, Jour. Acad. Nat. Sc. Phila. VIII, 1839, 101 .—Ib. in Townsend’s Narrative, 1839. 
Aud. & Bach. N. Am. Quad. I, 1849, 133 ; plate xv. 
Sp. Cn.—Much larger than Pteromys volucella. Tail, with hairs, longer than the body alone ; shorter than head and body. 
Flying membrane very broad, its antero-external corner exhibiting a conspicuous angle. Color above yellowish brown, 
beneath dull white ; the hairs plumbeous at base. Tail becoming more plumbeous towards the tip. Length, 7 inches; 
tail with hairs, 6J ; hind foot, 1J inches. 
This species is about the size of P. sabrinus, and considerably exceeds the P. volucella. The 
ears are large, their hack thinly coated with hair, their concavity nearly naked. The tail is 
long, and rather narrow hut depressed ; the sides nearly parallel; with the hairs, it is about as 
long as the body, exclusive of the head. 
In the only adult specimen I have seen, that described by Bachman, the spur on the fore leg 
supporting the flying membrane stands out at right angles to the wrist, carrying the membrane 
to a distance of about an inch and a quarter, (to the margin of the hairs,) when the outline 
bends abruptly at a right angle, (the corner rounded.) The exterior outlines of the membrane, 
when extended thus, diverge anteriorly, instead of being nearly parallel. 
The color of this species is of a dull yellowish brown above ; this color only on the tips of the 
hairs. The flying membrane above appears chiefly of a brownish plumbeous. The basal 
fourth of the tail above is colored like the back, and an obscure median stripe of the same 
extends nearly to the tip; the remainder of the upper surface has a plumbeous cast. The 
under parts are dull white; the hairs plumbeous at base, and mostly tipped with dirty 
yellowish brown. The under surface of the tail is nearly uniform light yellowish brown, with 
a tinge of plumbeous. 
Measurements. 
Inches. 
To root of tail .............._........___ 
7 
Tail vertebra_____ 
5f 
, hairs_ 
6£ 
Hind foot_...._____ 
1$ 
Expanse of flying membrane___ 
8 
The specimen from which this description is taken is the original of Dr. Bachman’s 
description, and now belonging to the Philadelphia Academy of Natural Sciences. Another 
specimen collected in California by Dr. Heerman, and presented by him to the Academy, is 
smaller, with a grayer or more hoary aspect above, though otherwise similar. 
Several very young squirrels, probably of this species, were obtained in Washington Ter¬ 
ritory by Dr. Cooper. 
List of specimens. 
Catalogue 
number. 
Corresponding 
No. of skull. 
Number of 
specimen. 
Sex and 
age. 
Locality. 
When col¬ 
lected. 
Whence and how 
obtained. 
Nature of 
specimen. 
599 
1,722 1 
. ____! 
2 
o 
o 
Washington Ter..... 
Ho 
1854 
1854 
Dr. J. G. Cooper .. 
.do.. 
Skin. 
Alcohol. 
