MAMMALS OF THE MEXICAN BOUNDARY. 369 



KEY TO EIGHT SPECIES AND SUBSPECIES OF ONYCHOMYS. 



a. Size large. Length, more than 150 mm; total length of skull, about 30 mm. 

 b. Size largest. Length, about 170 mm; tail vertebrse, 57 ; lund foot, 24. Color above, 



mouse-gray Onychomys longipes (p. 369.) 



56. Size smaller. Length, about 160 mm; tail vertebrae, 50; hind foot, 22. 

 t. Coloration very pale. Color above, pale tawny-cinnamon. 



Onychomys, paUescens (p. 371). 

 cc. Coloration dark. 



d. Color above, blackish slate (extralimital) Onychomys fuliginosus. 



dd. Color above, tawny-cinnamon Onychomys mdanophrys (p. 372). 



aa. Size small. Length, less than 150 mm; total length of skull, about 25.5 mm. 

 c. Coloration dark. 



/. Color above, tawny-cinnamon Onychomys torridus (p. 374) . 



ff. Color above, dark-grayish drab or mouse-gray. 



Onychomys torridus ramona (p. 379). 

 ee. Coloration very pale. 



g. Size smallest. Length, about 137 mm; tail vertebrae, 53; ear from 

 crown, 14; hind foot, 21. Skull, 25.5 by 13.5 mm. Color above, pale 



grayish drab .Onychomys torridus arenicola (p. 377). 



gg. Larger. Length, about 154 mm; tail vertebrsp, 56; ear above crown, 

 15; hind foot, 21.5. Skull,- 25.5 by 13.5 mm. Color above, pale drab- 

 gray Onychomys torridus perpaUidus (p. 378). 



ONYCHOMYS LONGIPES Merriam. 

 TEXAS GRASSEOFFER MOUSE. 



Onychomys longipes Merriam, North American Fauna, No. 2, Oct. 30, 1889, pp. 1, 2, 4, 

 and 5 (original description). — Miller and Rehn, Proc. Bost. Soc. Nat. Hist., 

 XXX, No. 1, Dec. 27, 1901, p. 66 (Syst. Results Study N. Am. Mam, to close of 

 1900). 



[Onychomys leucogaster]longipes,'E,iAAOT, Field Col. Mus., Zool. Ser., II, 1901, p. 120 

 (Synop. Mam. N. Am.). 



Type-locality. — Concho County, Texas. (Type, skin and skull, No. 

 fill, collection of Dr. C. Hart Merriam.) 



Geographical range. — Texas. Inhabits the Sonoran Zone from the 

 Gulf of Mexico west to Kinney County (Fort Clark) and north to 

 Fort Sill, Indian Territory (Dr. J. C. Merrill). 



Description. — Size, large (about the same as 0. melanophrys) . 

 Length, 170 mm.; tail vertebrae, 57 (to end of pencil, 61); ear, above 

 crown, 14.5; ear above notch, 18; length of hind foot, 23.5. Skull, 

 30 by 15.5; Coloration, dark; above, grayish drab, tingedwith cinna- 

 mon and mixed with black in the form of fine annulations and points 

 to the hairs, and with a narrow stripe of dull cinnamon along each 

 side, between the drab of the back and the white of the belly. Under 

 parts, feet, tip, and under side of tail, white. Ears dusky, with a 

 mixture of hoary at the tips, a black spot on the anterior border of 

 their outer surface, and with the woolly tuft at base, which is 

 30639 -No. 56—07 m 24 



