MAMMALS OF THE MEXICAN BOUNDARY. 



377 



ONYCHOMYS TORRIDUS ARENICOLA Mearns. 

 EL PASO GRASSEOFFER HOUSE. 



Onychomys torridus arenicola Mearns, Proc. U. S. Nat. Mus., XIX, 1896, p. 139 (p. 3 

 of advance sheet issued May 25, 1896; original description). ^Miller and 

 Rehn, Proc. Bost. Soc. Nat. Hist., XXX, Dec. 27, 1901, p. 67 (Syst. Results Study 

 N. Am. Mam. to close of 1900). 



[Onychomys torridus] arenicola, Elliot, Field Col. Mus., Zool. Ser., II; 1901, p. 122 

 (Synop. Mam. N. Am.). 



Olnychomys] f[orridus] arenicola, Elliot, Field Col. Mus., Zool. Ser., IV, 1904, pp. 165, 

 168 (Mam. Mid. Am.). 



Type-locality. — Bank of the Rio Grande, about 6 miles above the 

 town of El Paso, Texas. (Type, skin and skull, Cat. No. ||f f ^, U. S. 

 National Museum.) 



Geographical range. — Sonoran Zone of the Eastern Desert Tract. 



Description. — Slightly smaller than typical Onychomys torridus, with 

 relatively smaller ears and a much paler coloration. Above pale gray- 



FiG. 65.— Onychomys torridus arenicola. Skull of type, a, Dorsal view; b, Ventral view; 



c, Lateral view. ~ 



ish drab, with little mixture of black-tipped hairs; inclining to fawn 

 color on sides with & conspicuous tuft of white at anterior base of 

 ear; dark spot on anterior band of ear, dark drab instead of 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. Length, 137 mm. ; tail vertebrae, 53 (to end of pencil, 

 57); ear from crown, 14; ear from notch, 17; length of hind foot, 21. 

 Skull (fig. 65), 25.5 by 13.5. 



Remarhs. — This is the counterpart of 0. pallescens, of which it is 

 a miniature. The two are almost indistinguishable in color and 

 their ranges are probably coincident. The specimens of this species 

 taken west of the Rio Grande, for the first hundred miles, are small 

 eared, but otherwise closely resemble typica.1 torridus, to which 

 they are unhesitatingly referred. Specimen No. Vi¥, U. S. National 

 Museum, an exsimple of this form, was included by Professor Baird 

 in his "list of specimens of Hesperomys texanus." This specimen 

 was collected by Doctor Kennerly between the Pecos River and the 

 Rio Grande. 



