NO. 2057. THE GRASSHOPPER MICE—H0LLI8TER. 439 



maxillary tooth row, 4.4(3.9-4.6). For detailed measurements of 

 specimens see page 474. 



Type-specimen. — Regarding the specimens on which their descrip- 

 tion and figure were based, Audubon and Bachman say: 



This pretty little animal was discovered for us by Mr. Denig, during our sojourn at, 

 and in the neighborhood of Fort Union in 1843. It was in full summer pelage, hav- 

 ing been killed on the 14th of July. * * * The next day after they were brought 

 in, we left the fort on an expedition to the Yellow-Stone River * * * i. 



It is not known if, after the drawings were made, the specimens 

 were preserved or not. 



Remarks. — This subspecies is chiefly distinguished fo-om true le'w- 

 cogaster by its lighter color in all pelages. It attains its extreme 

 pallor in Saskatchewan, but is, on the whole, very uniform in color 

 over all the mapped range. Specimens from Dickinson, North 

 Dakota, show the nearest approach to leucogaster, but are distinctly 

 nearest to missouriensis. In the southeastern parts of its range, 

 missouriensis blends du-ectly into 0. I. articeps. 



Specimens examined. — Total number 62, fi-om localities as follows: 



AJlberta: Calgary, 2; Medicine Hat, 1. 



Saskatchewan: Carlton, 1; Osier, 3 (Mus. Comp. Zool.). 



Montana: Bozeman, 2; Fort Custer, 8; Fort Union, 1 ; Great Falls, 

 1 ; Johnson's Lake, 2 ; Mountain Sheep Buttes, 1 ; Pass Creek, 1 ; 

 Powderville, 1; Robare, 1; Tilyou's Ranch, 3. 



North Dakota: Buford, 8; Dickinson, 3; Fort Buford, 11; Glen- 

 uUin, 1. 



Wyoming: Ai-vada, 4; Little Powder River, 2; Moorcroft, 5. 



ONYCHOMYS LETTCOGASTER ARCTICEPS Rhoads. 



1896. Onychomys leucogaster brevicauda Allen, Bull. Amer. Mus. Nat. Hist., vol. 



8, p. 253. November 25. (Specimens from Wyoming and Colorado.) 

 1898. Onychomys arcticeps Rhoads, Proc. Acad. Nat. Sci. Philadelphia, 1898, p. 



194. May 3. 

 1907. Onychomys brevicaudus Gary, Proc. Biol. See. Washington, vol. 20, p. 25. 



March 27. 



Type-localiUj. — Clapham, Union County, New Mexico. 



Geographic distribution. — Upper Sonoran Great Plaius, from Wyo- 

 ming and South Dakota to Texas. North to the Big Horn River in 

 Wyoming and to the Cheyenne River in South Dakota; east to Bone- 

 steele, South Dakota, and Trego County, Kansas ; south to Fort Lan- 

 caster, Texas; and west to Bear River Divide in southwestern Wyo- 

 ming, Golden and Salida, Colorado, and Santa Rosa, New Mexico. 



General characters. — Like 0. I. missouriensis, but paler, more buffy 

 in color; much lighter than leucogaster, ruidosse, or Iremauritus. 

 Resembles 0. I. melanophrys but is less bright in coloration and is 

 slightly smaller, with smaller hind foot and ear. 



Color.— Adult in full pelage (18644, Valentine, Nebraska, April 14) : 

 Upperparts avellaneous, with a wash of brighter pinkish-cinnamon 



1 Viviparous Quadrupeds of North America, vol. 2, p. 328, 1851. 



