SCIURID^— SCIUEOPTERUS. 653 



Genus SCIUROPTERUS F. Cuvier 



Sciurus Linnaeus (in part), and of early authors generally. 

 Pteromya G. Cuvier (in part), and of most recent authors. 



Sciuropterus F. Cuvier, Ann. du Mus. x, 1825, 120, pi. x (typo, Sciurus volans Linn.); DeDts des Mani- 

 mileres, 1825, 162, 255. 



Generic chars. — Skull short, broad, highly arched, in general form almost 

 a miniature of that of Sciurus hudsonius; the supraorbital notch, however, is 

 rather deeper, and the interorbital region is rather more constricted ; the orbital 

 fossae are relatively larger, as are also the auditory bullae and the ears, in 

 conformity with the more nocturnal habits of the members of this group; 

 the pterygoid processes are more slender, and posteriorly touch the auditory 

 bulla?. In other particulars, the skulls of Sciuropterus and Sciurus present 

 no important differences. Premolars two, the first minute, but reaches the 

 plane of the trituration. Limbs united by a furred membrane formed by the 

 expansion of the skin of the sides of the body, and supported anteriorly by 

 a slender bone articulating with the carpus and directed backward. Tail 

 two-thirds as long as the head and body together, broad and flat, the longer 

 hairs being chiefly directed laterally, thus forming an important aid in govern- 

 ing the direction of their flight-like leaps, as well as serving as a further 

 means of support in their short flights from tree to tree. Sciuropterus is 

 thus merely a modified form of Sciurus, possessing rudimentary powers of 

 flight, through the support afforded by a parachute-like expansion of the skin 

 of the sides of the body and the broad, flat tail. The pelage is dense, soft, 

 and furry; the ears large and sparsely clothed; .the colors some soft, dull 

 shade of brown above and whitish beneath. Animals of small size, and of 

 crepuscular or nocturnal habits. 



The genus is represented in North America by a single species of wide 

 distribution, and presenting a very wide range of geographical variation in 

 size. A single species also represents the genus in Europe, but several other 

 commonly recognized species occur in Asia. The. Sciuropterus voluns of 

 Europe differs from the American S. volucella in its much smaller size and 

 relatively much shorter and smaller tail, as well as slightly also in color. 



The Flying Squirrels were first separated from ordinary Squirrels by G. 

 Cuvier* in 1800, he then giving to the group of Flying Squirrels the generic 

 name Pteromys. In 1825, his brother, F. Cuvier.t separated the small Flying 



* " Eecous d'anatomie coinparee, i, 1800." The original edition of this work I have heen unable to 

 consult. 



t Ann. du Mus., x, 1825, p. 126. See also Dents des Mammiferes, 1825, 162, 255. 



