168 ONYCHOMYS. 
TropicAL MoLe Mouse. 
Type locality, Camp Grant, Graham County, Arizona. 
Geogr. Distr. States of Chihuahua and Sonora, Mexico, north to 
Upper Missouri. 
Genl. Char, Similar to O. leucogaster; tail longer; ears larger; 
colors more yellowish. 
Color. General color more yellowish than O. leucogaster; no 
dorsal stripe; feet and under parts tawny white; tail above dusky, 
beneath white. 
Measurements. Total length, 70 tail vertebra, 51; hind foot, 20; 
ear, 19. Skull: Hensel, 18.5; zygomatic width, 12.5; interorbital 
constriction, 4.2; length of nasals, 9.6; length of upper molar series, 
3:5: 
a.—arenicola (Onychomys), Mearns, Proc. U. S. Nat. Mus., x1x, 
1896, p. 139. Elliot, Syn. N. Am. Mamm., 1go1, p. 122. 
SAND-LOVING MoLe Mouse. 
Type locality. Rio Grande near El Paso, El Paso County, Texas. 
Geogr. Distr. State of Chihuahua, Mexico, into Texas. 
Genl. Char. Similar to O. torridus, but slightly smaller, with 
relatively smaller ears and a very much paler coloration. 
Color. Above drab gray, inclining to fawn color on sides; dorsal 
area with very little admixture of black-edged or black-tipped hairs; 
a conspicuous tuft of white hairs at anterior base of ears; dark 
spot on anterior band of ear, drab (not black); whiskers more white 
than black; under parts, feet, and end of tail white; basal two- 
thirds of upper side of tail drab, some of the hairs with hoary tips. 
Measurements. Total length, 137; tail vertebrae, 53 (to end of 
pencil, 57); hind foot, 21. Skull: 25.513.5. (Mearns, 1. c.) 
b.—perpallidus (Onychomys), Mearns, Proc. U. S. Nat. Mus., xrx, 
1896, p. 140. Elliot, Syn. N. Am. Mamm., 1901, p. 122. 
Dras Gray Move Mouse. 
Type locality. Colorado River at Monument No. 204, Mexican 
boundary line, Yuma County, Arizona. 
Geogr. Distr. Lower California and State of Sonora, Mexico, to 
Gila City across Yuma and Colorado Deserts to Coast Range of 
Mountains, 
Genl. Char. Larger than QO. torridus, with relatively larger ears, 
longer tail, and a much paler coloration. 
Color. Above drab gray, becoming more cinereous anteriorly; 
sides and rump barely tinged with fawn color; dusky line on basal 
three-fourths of tail nearly obsolete, much obscured by whitish hairs; 
ears less densely clothed than in the other forms of O. torridus, and 
