nS PROCEEDINGS OF THE ACADEMY OF 



Subgenus Vesperimtjs, Cones. 



Stn. 3fmcului>, Raf., Am. Month. Mag. iii. 1818, 446 (used in connec- 

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

 omys, Baird (with exclusion of Onychomya and Oryzomyn^. 

 Calomys, Aud. and Bach. Q. N. A. ii. I80I, 303 (type aureolus ; not 

 of Waterhouse). 



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

 not beaded (compare Onychomys and Onjzomys). Coronoid not 

 attaining level of condyle. Cranial and dental characters in 

 general strictly those of Hesperomyn. Small but well-deA^eloped 

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

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

 rounded, thin, scantily and finely jnlous ; 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 6-tuberculate, 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. Pelade soft, close, 

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

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

 No woolly tufts of hair about the ears. Type, V. leucopus. 

 (Compare diagnoses of Onychomys and Oryzomys.) 



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

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

 having proven to my entire satisfaction the complete intergradu' 

 tion of the others. 



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



Syn. Aynerican Field 3fouse or Bat, Penn., Syn. 1771, No. 303; Hist. 



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

 American Wandering Mouse, Barton, Med. and Surg. Journ. Phila. i 



1805, p. 31. 

 Mus sylvatieus, var., Erxl., Syst. Av. i. 1775, 390 (based on "New 



York var." of Pennant). 

 JTus sylvKticus, var. noveboraceiuia, Fisch., Syn. 1829, 318 (the same). 

 Mus noBcboracetisis, Selys-Longch., Etudes Microm. 1839, 07. 

 Mus agrarius, var. americanus, Kerr's Linn. 1793, 231 (based on 



Pennant). 



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