VARIATIONS OF RODENTS 247 



farther posteriorly than do the nasals, which may prove to be a dis- 

 tinguishing character between boylii and nasutus. Certainly "length 

 of nose" in this particular population fails to be a criterion. The boylii 

 of the North Rim lack the globular bullae of P. truei. I have taken no 

 truei or nasutus in the Grand Canyon but Bailey ( 1935, p. 18) reported 

 the former "all through the Grand Canyon country, mainly in Upper 

 Sonoran Zone" and made no mention of nasutus. 



Neotoma cinerea acraia (Elliot) 



Habitat: Bushy-tailed wood rats appeared to be uncommon on the 

 North Rim. They were wary and the catch was low even where the 

 animals seemed to be concentrated. Evidence of their presence was most 

 abundant on rocky ledges just over the rim of the canyon where one 

 specimen was taken from a barren, weathered cliff on Point Honan and 

 two specimens (one subadult) came from a steep, rocky slope almost 

 covered with dense chaparral near Point Imperial. A young male was 

 unexpectedly trapped on Walhalla Plateau near Snowshoe Cabin under 

 a log on the bank of a small valley. There was no runway, tunnel, nest 

 or rock outcrop in sight. One sly adult was seen by day in an abandoned 

 cabin on Swamp Point but it could not be lured into a trap even in 

 several nights of trying. Signs of this species were also noted on a rocky 

 ledge near the Harvey Camp stables. 



Color: The young male from Walhalla Plateau was acquiring its 

 adult pelage which seems unusually pale for this area as well as for this 

 species. Buff shows brightly on face, sides, shoulders and hips. The 

 lumbar region is pale gray, and there is a broad, midventral white stripe, 

 the hairs of which are white to the base. The tail is only slightly bicolor 

 with a faint, yellow-tinged, gray dorsal stripe. The short lateral and 

 ventral hairs of the tail are white. Such a pelage seems more appropriate 

 for an animal living in the Lower Sonoran Zone, e.g., in the Painted 

 Desert across the Colorado River. However, the absence of sphenopala- 

 tine vacuities distinguishes this specimen from the bushy-tailed wood 

 rats (A^ c. arizonae) in the desert to the southeast. Hall (1931, p. 6) 

 stated that the color of pelage in these rodents seems particularly respon- 

 sive to climatic conditions. Two pale specimens, one of A^. c. acraia 

 (Kelson, 1951, p. 94) and one of A^. c. arizonae (Durrant, 1952, p. 352) 

 were reported from Utah. !My pale specimen from the North Rim may be 

 an extreme color variant of the high montane population but is more 

 probably a migrant from the Sonoran Life Zone of the wall of the 

 canyon up to this high plateau valley. My other specimens from the 



