G56 MONOGRAPHS OF NORTII AMERICAN RODENTIA. 



Specific chars. — Size varying greatly with locality. Head and body 

 ranging, in adults, from 7 50 to 4.75 inches; tail-vertebrae from 5.00 (or a 

 little more) to 3.50; tail, with hairs, from about 6.50 to 4.25 (occasionally 

 less). Above yellowish-brown, varying to pale reddish-brown; below white, 

 varying to creamy-white, with sometimes a faint tinge of pale rufous; tail 

 above generally darker than the back, especially at northern localities, where 

 it is sometimes decidedly blackish ; tail below lighter than above, varying 

 with locality from dusky-brown to yellowish-brown, always more strongly- 

 colored than the ventral surface of the body. 



Var. hudsonius. 



Northern Flying Squirrel. 



Varietal chars. — Length, exclusive of the tail, G.OO inches or more; 



tail, with the hairs about 5.00. Above dull yellowish- or reddish-brown; 



below white, faintly washed with yellowish; tail above dusky, often decidedly 



blackish on the edges and terminal half; also frequently dusky toward the 



end below. Habitat mostly north of the parallel of 49°, extending further 



southward along the Rocky Mountains and on the Pacific slope. Grades 



insensibly into — 



Var. VOLUCELLA. 



Southern Flying Squirrel. 



Varietal chars. — Similar to the preceding, but much smaller. Length, 

 exclusive of the tail, less than 6.00 inches; generally less than 5.50. Tail 

 less dusky, often with no blackish whatever, and the general color of the 

 body above rather more yellowish. Habitat, United States, — exclusive of 

 the Pacific slope north of California, and the Rocky Mountains north of Col- 

 orado ; and thence southward to Guatemala. 



The American Flying Squirrels present a range of geographical varia- 

 tion in size quite unparalleled in other members of the Sciuridce, and only 

 equalled in some species of the Canidce, and possibly in Cervus virginianus. 

 On the other hand, the coloration is remarkably constant, almost exception- 

 ally so, no other North American Mammal with which I am acquainted, 

 which has so wide a geographical range, varying so little in this respect witli 

 locality. The species ranges from Arctic America into the tropical portions 

 of the continent. I have specimens before me from points as distant as 



