10 



Subgenus Vesperimus, Coues. 



Syn. Munculux, Raf., Am. Month. Mag. iii. 1818, 446 (used in connec- 

 tion -with leucopus, but ineligible for obvious reasons.) — Hesper- 

 omys, Baird (with exclusion of Onychomys and Oryzomys<). — 

 Cdlomys, And. and Bacli. Q. N. A. ii. 1851, 303 (type aureolus ; not 

 of Waterhouse). 

 Char. Teeth strictl}' sigmodont. Back upper border of orbit 

 not beaded (compai-e Onyohomtjs and Oryzomys). Coronoid not 

 attaining level of condyle. Cranial and dental characters in 

 general strictly those of Hesperomya. Small but well-developed 

 cheek-ponches! Of medium and small size, lithe form and quick 

 movement. Eyes large, prominent. Snout pointed. Ears large, 

 rounded, thin, scantily- and finely pilous ; antitragus evident but 

 not valvular. Fore feet hardly or not half as long as the hinder; 

 palms naked ; fore claws not larger than the hinder ; digits slender, 

 3d and 4th subequal and longest, 2d and 5th successively much 

 shorter. Hind feet long, slender; soles G-tubdrculate, naked or 

 scant-furred on the posterior third ; 2d, 3d, and 4th subequal 

 and much the longest, 5th shorter; 1st shortest. Tail terete, 

 slender, closely hairy, ranging in length from as long as body 

 alone to a little longer than head and body. Pelage soft, close, 

 glossy, with but few longer bristly hairs ; feet and under parts 

 white or whitish ; body and tail more or less distinctly bicolor. 

 iVo woolly tufts of hair about the ears. Type, V. leucojnn^. 

 (Compare diagnoses of Onychomys and Oryzomys.) 



Obs. Among the multitude of species of this group ascribed to 

 North America, I can recognize as distinct but the few following, 

 having proven to my entire satisfaction the complete intergrada- 

 tion of the others, 



1. Hesperomys (Vesperimus) leucopus, (Raf.) Le Conte. 



Syx. Americim Field Mouse or B'(t, Penn., Syu. 1771, No. 303; Hist. 

 Quad. 1781, No. 302 ; Arct. Zool. i. 1784, 131. 

 Americm Wandering Mouse, Barton, Med. and Surg. Journ. Pliila. i 



1805, p. 31. 

 Mm Hylvdticm, var., ErxL, Syst. Av. i. 1775, 390 (based on "New 



York var." of Pennant). 

 Mus sylvnticus, var. 7ioveboracensis, Fisch., Syn. 1829, 318 (the same). 

 Mus noveboraceiisis, Selys-Longch., Etudes Microm. 1839, G7. 

 Mus agrarius, var. umericanus, Kerr's Linn. 1792, 231 (based on 

 Pennant). 



