scnxRiD^. — X. 27 



distinct. Species of rather small size, widely distributed. 

 The variations in color, etc., are extremely great, and 

 the number of well-defined species is very much less 

 than was once supposed. 



* A densely furred membrane extending along the sides between 

 the anterior and posterior limbs; tail depressed, flattened, 

 densely furred ; permanent molars 5-5 above. 



SOTOBOPTEKUS, 1. 



** Sides without membrane for " flying." 



t No cheek pouches; tail bushy, at least as long as body; ears 

 long ; no black stripes along the back. . Sciubus, 3. 

 ff Cheek pouches present. 

 X Back with 3 to 5 distinct black stripes ; tail shorter than 

 body, not bushy; cheek pouches well developed. 



Tamias, 3. 

 ff Not as above; body rather slender, squirrel-like; cheek 

 pouches well developed; claw of thumb rudimentary 

 or wanting. .... Spermophilus, 4. 

 ttt Body large, thick-set, depressed ; cheek pouches shallow ; 

 thumb rudimentary, armed with a small flat nail, not a 

 claw; soles naked. . . . Abctomys, 5. 



/. SCIUROPTERUS, F. Cuvier. Plying Squirrels. 



< Pteromys^ Cuvier. 



1. S. volucella, (Pall.) Geoff. Common Flying 

 Squirrel. Yellowish brown, creamy white below. N. 

 Am., abundant. {P. volucella, etc., authors.) 



2. SCIURUS, Linnaeus. Squirrels. 



1. S. niger, Linn. Fox Squirrel. Upper molars 

 permanently 4; tail very large and bushy; general color 

 rusty gray, varying from almost white, through various 

 shades of rusty red to jet black, the latter color rare 

 northward, reddish and orange shades predominating 

 westward; L. 36; T. 14. E. U. S., very abundant in the 



