ROUENTIA SCIURINAE PTEROMYS ALPINUS. 



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List of specimens. 



PTEROMYS ALPINUS. 



Rocky Mountain Flying Squirrel. 



Plerwnys sabrinus, var. /? 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. 



ACD. & BACH. N. Am. Quad. HI, 1853, 206 ; plate cxliii, fig. 2. 



SP. CH. Larger than P. taMnus. 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. 

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