290 U. S. P. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



PTEROMYS OREGONEN6IS, Bach. 







Columbia River Flying Squirrel. 



Ptfromys oregonensis, BACHMA*, Jour. Acad. Nat. Sc. Phila. VIII, 1839, 101. IB. in Townsend's Narrative, 183!>. 

 AUD. & BACH. N. Am. Qnad. I, 1849, 133 ; plate XT. 



g p> C H . Much larger than Pteromys voluceUa. Tail, with hairs, longer than the body alone ; Bhorter than head and l>o< y. 



Flying membrane very broad, its antero-external corner exhibiting a conspicuous angle. Color above yellowish brov*n, 

 beneath dull white ; the hairs plumbeous at base. Tail becoming more plumbeous towards the tip. Length, 7 inchts; 

 tail with hairs, 6J ; hind foot, 1 J inches. 



This species is about the size of P. sdbrinus, and considerably exceeds the P. voluceUa. The 

 ears are large, their back thinly coated vriih hair, their concavity nearly naked. The tail is 

 long, and rather narrow but depressed ; the sides nearly parallel ; with the hairs, it is about ;is 

 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 tie 

 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 san e 

 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. 



To root of tail _ . 



Tail vertebra) 



, hairs 



Hind foot 



Expanse of flying membrane. 



Inches. 



7 



5J 



6* 



The specimen from which this description is taken is the original of Dr. Bachman' 8 

 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. 



