VOL. VIII, PP. 55-70 JUNE 20, 1893. 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON. 



DESCRIPTION OF A NEW WHITE-FOOTED MOUSE 

 FROM THE EASTERN UNITED STATES. 



BY GERRIT S. MILLER, JR. 



A critical study of over five hundred specimens of Sitomys 

 collected in the northeastern United States and adjoining British 

 provinces leads me to the conclusion that two distinct though 

 somewhat closely related animals are at present confused under 

 the name of Sitomys amerieanus. The two forms may be distin- 

 guished by the following diagnoses : 



Ratio of tail vertebrae to total length ranging from 40 to 47.9 ; 

 pencil, 2 mm. to 5 mm.; tail often not sharply bicolor; young 

 usually passing directly from the plumbeous first coat to the 

 russet-brown pelage of the adult, which is thus present in the 

 great majority of specimens amerieanus. 



Ratio of tail vertebra) to total length ranging from 46.5 to 53.6 ; 

 pencil, 4.4 mm. to 11 mm.; tail always sharply bicolor; young 

 always passing through a gray phase between the plumbeous 

 first coat and dull yellowish brown pelage of adult, which is 

 thus comparatively seldom met with. . . . canadensis. 



Sitomys amerieanus canadensis subsp. nov. 



Hesperomys myoides Baird. Mam. N. Am., 1857, 472 (probably in part 

 only), not Cncetus myoides Gapper. 



Subsp. Ch. Somewhat larger than Sitomys awr Tirana A (Kerr), 

 with longer, more hairy tail, and duller, less russet coloration,; 



8 BIOL. Hoc. WASH., VOL. VIII, 189IJ. (55) 



