456 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 47. 



Suhs2)ecies. — Eleven geographical races of Onychomys torridus are 

 recognized. Four of these are confined to Mexico, and the others, 

 with the exception of typical torridus, have comparatively limited 

 distribution. 



ONYCHOMYS TORRIDUS TORRIDUS (Coues). 

 1874. Hesperomys (Onychomys) torridus Coues, Proc. Acad. Nat. Sci. Philadel- 



pliia, 1874, p. 183. December 15. 

 1885. Onychomys leucogaster, var. torridus Herrick, Geol. and Nat. Hist. Surv. 



Minnesota, 13th Ann. Rep. (1884), p. 183. 

 1885. Hesperomys torridus True, Proc. U. S. Nat. Mus., vol. 7 (1884), p. 597. 



1888. C[ricetus] torridus Thomas, Proc. Zool. Sue. London, 1888, p. 133. 



1889. Onychomys torridus Merriam, North Amer. Fauna, No. 2, p. 3. October 30. 

 1896. Onychomys torridus arenicola Mearns, Proc. U. S. Nat. Mus., No. 1103, 



advance sheet, p. 3, May 25; Proc. U. S. Nat. Mus., vol. 19, p. 139. (Pdo 

 Grande, about six miles above El Paso, Texas; type in IT. S. Nat. Mus.) 

 1912. Onychomys torridus torridus Miller, Bull. 79, U. S. Nat. Mus., p. 128. 

 December 31. 



Type-locality. — Camp Grant, Graham County, Arizona. 



GeograpUc distribution. — From the Pecos Valley in Texas and south- 

 eastern New Mexico, west across southern New Mexico and Chihuahua 

 into southeastern Arizona and northern Sonora. North in the Rio 

 Grande Valley to Socorro, New Mexico; south to northern Durango. 



General characters.— Size medium, but less than in any neighboring 

 form; ear smaller than in any other subspecies of torridus. Color of 

 adult in late autumn and winter very rich reddish brown; much paler 

 in late winter and spring; and darker, less bright, in the new coat in 

 late summer; young very dark. Skull with the anterior palatine 

 foramina large, extending backward to plane of anterior edge of m\ 

 or beyond to plane of second cusp of this tooth; posterior edge of 

 palate normally concave, without projecting spine. 



Color.— Adult in full winter pelage (17876, Dos Cabezos, Arizona, 

 November 21): Upperparts dark pinkish-cimiamon, rich and glossy; 

 palest on the nose and cheeks; darkest along back from between 

 ears to rump, where it is considerably mixed with the dark blackish- 

 brown tips of the long overlying hairs; purest and brightest on 

 shoulders and sides where there is little or no admixture of blackish. 

 Whiskers mixed black and white; underfur broadly dusky neutral- 

 gray; lanuginous tufts in front of ears conspicuous, pure white; outer 

 ear dark brownish, rimmed with whitish; inner side of ear scantily 

 haired with whitish. Underparts pure white, sharply cut off from 

 color of upperparts, and extending well up on lower sides of body 

 and on lower cheeks; the underfur for one-half its length dark 

 neutral-gray, black in some lights; arms and hands pure white; legs 

 like hips above, white below; feet white. Tail sharply bicolor, gray- 

 ish-brown above to near tip; white below and around tip. Adult in 

 late winter and spring (21201, Mesquite Springs, Chihuahua, May 12): 

 Much paler than in full winter coat, less reddish-cinnamon, more 



