468 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.47. 



ONYCHOMYS TORRIDTJS RAMONA Rhoads. 



1893. Onychomys ramona Rhoads, Amer. Nat., vol. 27, p. 833. September. 

 1904. Onychomys torridus ramona Merriam, Proc. Biol. Sec. Washington, vol. 17, 

 p. 124. June 9. 



Type-locality. — San Bernardino Valley, California. 



GeograpMc distribution. — Extreme southwestern California and 

 northwestern Lower CaHfornia, Mexico. From San Fernando and 

 San Bernardino south into Tecarte Valley. 



General characters. — Size slightly greater than in 0. t. pulcher; 

 coloration very dark, the darkest of all the forms of the torridus group 

 found in the United States; skull like that of pulcher. 



Color. — Adult in full winter pelage (126063, Mouth of Tia Juana 

 River, California, January 18): Nose, head, and broad area along 

 upperparts to base of tail blackish-brown; sides of body and outer 

 sides of hind limbs to ankles brighter, more reddish-brown, with less 

 admixture from dark hair tips; ear tufts mixed brown and whitish, 

 not especially conspicuous; underparts creamy- white, the hairs of 

 chin and throat without grayish undercolor. Tail blackish-brown 

 above, whitish at tip and below. Adult in early summer (127979, 

 Reche Canyon, California, May 24) : Lighter, more reddish, than in 

 winter, without definite dark area on dorsum, the blackish-brown 

 hair tips having faded and worn away. The most extreme example 

 of this stage that I have seen is number 7376 of the Museum of Ver- 

 tebrate Zoology, University of California, from Jacumba, March 19. 

 It is the brightest specimen of ramona in all the collections, and most 

 resembles specimens of true torridus in full winter pelage. Juvenile 

 pelage (34090, San Diego, CaHfornia, May 10): Darker than young 

 of pulcher, more mouse-gray above. Post-jwvenile pelage (31075, 

 Reche Canyon, September 22; apparently in second year): Upper- 

 parts light drab, darker, more grayish, on head and lower back. 



Slcull. — The skull is apparently indistinguishable from that of 0. t. 

 pulcher. (Plate 15.) 



Measurements. — Averages and extremes of 10 adult specimens: 

 Total length, 141 (137-148) millimeters; tail vertebrae, 49.5 (36-56); 

 hind foot, 20.3 (19.0-21.0); ear from notch in dry skin, 14.7 (14.2- 

 15.4). Skull: Condylobasal length, 23.4 (22.6-23.8); zygomatic 

 breadth, 13.2 (12.7-13.7); interorbital breadth, 4.8 (4.6-5.0); breadth 

 of braincase, 11.8 (11.4-12.3); length of nasals, 9.7 (9.2-10.1); length 

 of mandible, 13.6 (13.2-14.0); maxillary tooth row, 3.6 (3.4-3.7). 

 For detailed measurements of specimens see page 482. 



Type-specimen. — No. 7823, collection of Academy of Natural 

 Sciences, Philadelphia. Skin and skull of female adult (teeth con- 

 siderably worn), in early summer stage of pelage, with dark dorsal 

 area nearly obsolete and general color considerably paled. Collected 

 April 11, 1893, by R. B. Herron. Original number, 218 (Rhoads 

 collection. No. 823). 



