SCIUROPTKRUS 941 



Genus SCIUROPTERUS F. Cuvier. 



1825. Sciuropterus F. Cuvier, Dents des Mammiferes, p. 255. 

 1857. Pteromys Blasius, Saugethiere Deutschlands, p. 268. 



Type species. — Sciurus volans Liniiieus = Pteromys russicus 

 Tiedemann. 



Geographical distribution. — As in the family. 



Characters. — No membrane extending between tail and hind 

 leg ; structure of molars essentially as in Sciurus, the enamel not 

 thrown conspicuously into wrinkles, the transverse ridges well 

 developed ; posterior upper premolar about as large as first molar, 

 never decidedly smaller. 



ItemarTis. — The genus Sciuropterus as thus defined contains 

 about thirty species, most of them Malayan. It is divided into 

 four sub-genera, to one of which (Glaucomys) belong all the 

 American members of the family. The single European repre- 

 sentative of the group is the type of the sub-genus Sciuropterus, 

 the three or four other known members of which occur in central 

 and northern Asia and in Japan. 



SCIUROPTERUS RUSSICUS Tiedemann. 



1758. [Sciurus] volans Linuseus, Syst. Nat., i, 10th ed., p. 64 (Sweden). 



Not Mus volans Linnseus, I.e., p. 63. 

 1808. P[teromys'] russicus Tiedemann, Zoologie, i, p. 451 (Russia). 

 1822. Pteromys sibiricus Desmarest, Mammologie, ii, p. 342 (Substitute 



for volans). 

 1843. Pt[eromys'] vulgaris Wagner, Schreber's Saugthiere, Suppl., in, p. 228 



(Substitute for volans). 

 1857. Pteromys volans Blasius, Saugethiere Deutschlands, p. 269. 

 1903. Sciuroptertis russicus Allen, Bull. Amer. Mus. Nat. Hist., xix, p. 132. 



March 31, 1903. 

 1910. Sciuropterus russicus Trouessart, Faunc Mamm. d'Europe, p. 116. 



Type locality. — Russia. 



Geographical distribution. — Wooded portions of northern 

 Siberia and Russia, southward nearly to the boundary of north- 

 eastern Germany, eastward into northern Scandinavia. 



Diagnosis. — Size median (head and body about 170 mm., tail 

 about 110, hind foot about 33, condylobasal length of skull 

 about 37) ; colour of upper parts a light silvery or buffy grey ; 

 skull with nasals abruptly constricted just behind middle, not 

 narrowing gradually backward ; auditory bulla very large, its 

 greatest antero-posterior diameter equal to distance between 

 bulla and anterior portion of first molar. 



External characters. — Form not essentially different from that 

 of Sciurus vulgaris, but appearing broadened and flattened on 

 account of the more depressed tail and the wide flying membrane. 

 Head short and round ; eyes xevy large ; ear low,' rounded, 

 almost concealed in the fur, the outer margin faintly concave 



