448 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.47. 



in coloration and intergradation presumably takes place at all 

 places where the lava-bed form meets the desert race. 



Specimens examined. — Total number, 5, from the following 

 localities : 



Arizona: Black Tank, Painted Desert, 3, including the type; San 

 Francisco Mountain, cedar belt, east side, 2. 



ONYCHOMYS LETTCOGASTER RTJIDOS^ Stone and Rehn. 



1903. Onychomys ruidosse Stone and Rehn, Proc. Acad. Nat. Sci. Philadelphia, 



1903, p. 22. May 7. 

 1913. Onychomys leucogaster ruidosse Hollister, Proc. Biol. Soc. Washington, 



vol. 26, p. 216. December 20. 



Type-locality. — Hale's Ranch, Ruidoso, Lincoln County, New 

 Mexico. 



Geograpliic distribution. — Chiefly the mountainous region of south- 

 eastern Arizona and central and southwestern New Mexico. North 

 to Camp Verde, Arizona, and to the Manzano Mountains and Las 

 Vegas, New Mexico; east to the Capitan Mountains; south into north- 

 ern Chihuahua and Sonora. 



General characters. — A dark form of the melanophrys type; darker 

 and richer colored than m,elanopTirys, arcticeps, or albescens, its geo- 

 graphical neighbors ; never, apparently, in its typical form, attaining 

 the light buffy state of coloration. 



Color. — Adult in full fall pelage (119149, Carrizozo, New Mexico, 

 October 30): Above glossy dark wood-bro^vn, with a wash of rich 

 cinnamon color and finely lined with darker brown hair tips ; darkest 

 on lower back and rump, palest on shoulders and sides; posterior 

 sides of body and hips almost pure cinnamon. Ear tufts pale cin- 

 namon-brown, inconspicuous; ear brownish outside, rimmed with 

 white; posterior side of inner ear with pure white hairs; tail grayish- 

 brown above, whitish at tip and below. Lips, arms, hands, feet, 

 and entire underparts whitish. Juvenile (119151, Carrizozo, New 

 Mexico, October 31): Almost exactly like corresponding age in 0. I. 

 longipes, but tail lighter above, pale gra3ash-brown. Young adult 

 in autumn (119152, Carrizozo, New Mexico, October 31): Paler and 

 less richly colored than old animals. Above drab, very finely 

 streaked with darker, and lightly washed with pale cinnamon. 



Specimens collected during process of renewal into first full adult 

 pelage are often curiously and irregularly mottled, with the head and 

 dorsum dark brownish and the shoulders and sides patched with 

 bright cinnamon. 



SlcuU. — Less high and elongated than in albescens and longipes; 

 much as in arcticeps, mth flattened braincase. Differs from the skull 

 of arcticeps, however, in its wider, less parallel sided, interpterygoid 

 space and slightly smaller audital bullae. (Plate 15.) 



