460 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.47. 



County, Arizona, March 27): Paler and more grayish than in late 

 autunin and midwinter, lacking much of the bright pinkish tmt. 

 General color of upperparts vmaceous-buff, finely streaked by the 

 darker hair tips; ear tufts not noticeable. Adult in summer (16855, 

 PhoenLx, Ai-izona, May 9): Like late winter and spring specimens 

 but more cinnamon colored, less grayish, chiefly due to the wearing 

 away of the dark hair tips of the old pelage and the gradual renewal 

 of the new hairs. This stage more closely resembles the full winter 

 coat than the last described spring stage in color, but is more cm- 

 namon, less pinkish. Juvenile (141849, Gila City, Arizona, March 

 3): Very much paler than the young of torridus, drab instead of 

 gray. Upperparts light drab, paler and clearer on sides; underparts 

 white [not gray as in juvenile of torridus], the hairs of throat pure 

 white to bases, of breast and belly with narrow gray undercolor. 

 Post-juvenile pelage (189288, Yuma, Arizona, April 11): This pelage 

 is retained by most individuals until late spring of the second year. 

 It is much like the post-juvenile pelage of true torridus, but slightly 

 paler, more grayish. Upper parts avellaneous, finely and fully 

 streaked by the darker hair tips. 



Shull. — The skull is like that of torridus, but with the posterior 

 border of palate bow-shape, always with well-developed point ex- 

 tending backward into the mterpterygoid space; anterior palatine 

 foramina shorter, usually just reaching plane of fronts of fh'st molars. 



Measurements. — Type: Total length, 157 millimeters; tail verte- 

 brge, 57; hind foot, 22.0; ear from notch in dry skin, 15.8. Average 

 and extremes of four skulls of adults: Condylobasal length, 24.1 

 (23.5-25.3) ; zygomatic breadth, 13.0 (12.7-13.2) ; interorbital breadth, 

 4.6 (4.4-4.7) ; breadth of braincase, 11.4 (11.3-11.5); length of nasals, 

 9.9 (9.4-10.5); length of mandible, 13.8 (13.5-14.2); maxillary tooth 

 row, 3.8 (3.7-4.0). For detailed measurements of specimens see 

 page 481. 



Type-specimen. — No. 60174, United States National Museum. 

 Skin and skull of adult female, in late winter pelage. Collected 

 March 27, 1894, by Dr. Edgar A. Mearns and F. X. Holzner. No. 

 3301, International Boundary Commission collection. 



Remarlcs. — This well-marked form seems to be confhied to the 

 east side of the Colorado River, in western Arizona, and eastward 

 along the Lower Sonoran valleys of tributary streams. As sho^^Ti 

 by the specimens at hand, its range reaches its most eastern limit 

 in the valley of the upper Gila at PhoenLx, Ai-izona. Specimens 

 from Phoenix, in full fresh early winter coat, almost exactly match 

 m color the paler spring stage of true torridus. The Colorado River 

 seems a natural barrier between the ranges of perpallidus on the 

 east, and pulclier and longicaudus on the west and north. Although 

 specimens from points near the river in northwestern Arizona and 



