132 



GENUS PTEROMYS.— Illiger. 



DENTAL FORMULA. 



Incisive 5 ! Molar j— r = 22. 

 £ 4—4 



Dentition similar to that of the genus Scnmus. Head, round; ears, 

 round ; upper lip, divided ; eyes, large ; fore-feet, with four elongated 

 toes, furnished ■with, compressed, sharp, talons, with the rudiment of a 

 thumb having an obtuse nail ; hind-feet, with five long toes, much divid- 

 ed, and fitted for seizing or climbing ; tail, long, villose ; skin of the sides, 

 extending from the anterior to the posterior extremities, forming a thin 

 membrane, by the aid of which, when extended, the animal sails through 

 the air in a descending curve from a tree or any elevated point, occasion- 

 ally for some distance. 



The generic name pteromys is derived from two Greek ■«'ords, mfta, 

 (pteron,) a wing, and fcvi, (mus,) a mouse. 



There are thirteen well-determined species belonging to this genus. 

 One is found in the north of Europe, four in North America, and the re- 

 mainder in Asia and other parts of the old world. 



PTEROMYS OREGONENSIS.— Bachman. 



Oeegon Flying Squikeel. 

 PLATE XV. — Male and Female. — ^Natural size. 



P. magnitudine inter P. volucellam et P. sabriniun medius, supra fus- 

 cus, subtus luteo-albus ; auribus P. sabrini auriculis longioribus ; vellere 

 densiore, membrana volatica largiore, pedibus grandioribus. 



CHARACTERS. 



Intermediate in size between P. volucella, and the Northern species, P. sa- 

 brinus ; ears, longer than in the latter, and far more compact ; lobe of the 

 flying membrane joining the fore-feet, much longer in proportion ; making 

 that membrane broader. Foot larger ; general colour above, brown ; be- 

 neath, yellowish-white. 



