SCIURIDE—SCIUROPTERUS VOLUCELLA. 661 
cella, it having been previously referred by Linneeus to the Flying Squirrel 
of Europe (Sciurus volans Linn. =Sciuropterus volans F. Cuv.). Richardson, 
in 1828, described a variety of the Northern Flying Squirrel, from the 
uorthern portion of the Rocky Mountains, under the name Péeromys 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 adpinus 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”. 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 Americasthe present species (P. sabrinus) and the little 
LP. 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. 
