1911] Taijlor: Mammal.'^ of the 1909 Nevada Expedition. 275 



Cranial characters of the series are those of olivaceus, al- 

 though in none of the skulls do the auditory bullae meet anter- 

 iorly, even in a weak symphysis. 



A small series of Perog)iat]ius p. niollipilosus Cones (type 

 locality Fort Crook, Shasta County, California), from i\Iount 

 Shasta, is contained in the JMuseum collection. That this form 

 does evince a tendency to approach olivaceus, as remarked by 

 Osgood (1900, p. 37), is evidenced by the fact that were the 

 specimens of mollipilosus to be mixed with the series from Nevada 

 it would be impossible to segregate the animals by their colora- 

 tion. The most practical differential character appears to be size, 

 olivaceus being larger. 



As exemplified by our series, Pcrogiiafhiis p. olivaceus dif- 

 fers from P. p. parvus (Peale), type locality, The Dalles (?), 

 Oregon, in having the ventral hairs normally white instead of 

 huffy. In size olivaceus is slightly greater. The species ap- 

 proaches parvus in a tendency to have the proximal fourth of the 

 sole of the hind foot haired. Tail, ears and subaurical spot as in 

 parvus. The two subspecies are evidently closely allied. 



P. p. olivaceus is immediately distinguished from P. p. magru- 

 derensis Osgood, type locality, 8000 feet altitude, ]\Iount ^lagru- 

 der, Nevada, at least as far as our specimens are concerned, by its 

 much smaller size. 



Certain individual peculiarities of pelage deserve mention. 

 No. 8125, an adult male, trapped June 2, at Quinn River Cross- 

 ing, is molting into the post-breeding pelage. The line separating 

 the new hair from the old is distinct at about two-thirds of the 

 distance from head to tail. The new pelage does not differ 

 appreciably in color from the breeding coat. The molt appears 

 to have proceeded uniformly from before backward. In no. 8121, 

 breeding female, taken ]\Iay 18, at the same locality, the new 

 pelage is darker and less buffy than the old. No. 8150, adult 

 female, secured August 8, on Leonard Creek, has the molt uneven, 

 and the pelage patchy. In no. 8135, adult male, taken on June 

 13 at Big Creek Ranch, the molt has progressed most rapidly 

 dorsally, and has reached the tail medially, but not on the sides. 

 No. 8124, breeding female, Quinn River Crossing, ]\lay 2H, also 

 shows a distinct molt-line. In the others (with the exception of 



