SCIURID^E— SOIUROrTERUS VOLUGELLA. 661 



cclla, it having been previously referred by Linnaeus to the Flying Squirrel 

 of Europe (Sciurus volans Ijmri.—Sciuropterwvolans F. Cuv.). Richardson, 

 in 1828, described a variety of the Northern Flying Squirrel, from the 

 northern portion of the Rocky Mountains, under the name Pteromys sabrinus 

 var. alpinus. Later, however, he was in doubt as to whether the differences 

 observed merited recognition. Wagner, however, in 1843, raised Richard- 

 son's variety alpinus to specific rank, since which time it has passed generally 

 current as a species, being so recognized by Audubon and Bachman, and 

 later by Professor Baird. Bachman, in 1839, described specimens from near 

 the mouth of the Columbia River under the name Pteromys oregonensis, and 

 this name has since passed generally current as that of a valid species. The 

 differences supposed to characterize it were, however, slight, consisting, in 

 reality, only in its rather smaller size as compared with P."sabrinus v . From 

 P. " volucella'' it differed in being larger, and in not having the hairs of the 

 ventral surface white to the roots, as Dr. Bachman erroneously supposed to 

 be always the case in the Southern Flying Squirrel. Thus originated the 

 four supposed species of North American Flying Squirrels. Ten years later, 

 however, we find the following suggestive remarks in Audubon and Bach- 

 man's ''Quadrupeds of North America" (vol i, p. 205), under the head of 

 P. "sabrinus'' : — "As long as only two species of Flying. Squirrels were 

 known in North America — the present species (P. sabrinus) and the little 

 /'. volucella — there was no difficulty in deciding on the species, but since 

 others have been discovered in the far West, the task of separating and defin- 

 ing them has become very perplexing." 



Professor Baird, in 1858, having few specimens of the group at hand 

 for comparison, admitted all of the four species, but evidently with some 

 hesitation. P. " volucella''' seemed to him to be only a miniature of P. "hud- 

 sonius'', the only differences perceivable to him being the larger size of the 

 latter, with the hairs of the belly lead-colored at base instead of white 

 throughout. Respecting the distinctness of P. "alpinus'' from P. " hudsonius" ', 

 he felt unable to decide, while the validity of P. "oregonensis" was apparently 

 not questioned. 



