288 PROCEEDINGS OF THE ACADEMY OF 



the end, and with long terminal pencil of hairs. Soles distinctly 

 naked to the heels, at least along a median strip. Antitragus 

 distinctly lobed, with a sharp teat-like projection, opposite which 

 is another smaller but distinct lobe of the tragus, the notch of the 

 ear being defined by these two prominent points, the edge of the 

 ear itself not bounding the notch at all. No appreciable fulvous 

 stripe along the sides, where the color of the upper parts meets 

 the white of the under parts without intervention of a third color. 

 Above, gray; an intimate mixture of yellowish-gray with a dull 

 grayish-brown; below, including whole fore leg, fore and hind 

 feet, and inner aspect of thighs, white ; tail bicolor dark above, 

 white below. Length about 3.25 inches (2.90-3.60) ; tail vertebrae 

 about 4.00 (3.50-4.40), with a tuft half an inch or more longer. 

 Soles about 0.95 (0.90-1.00) ; ear above notch, 0.33 (0.30-0.35). 



Hab. The basin of the Colorado River. (The very few speci- 

 mens at present known to naturalists have all come from Arizona 

 and the adjoining border of Southern California.) 



Description (from Woodhouse's type (mounted), and several 

 more recent specimens, dry and in the flesh). In all the other 

 species of Perognathm given on these pages the tail, whether longer 

 than the body or decidedly shorter, is simply haired, with the 

 terminal hairs no longer than those surrounding the tail. The 

 present species is therefore remarkably distinguished by the comb 

 or crest of long hairs on the terminal third or more of the member, 

 produced b}- a gradual lengthening until those at the end are half 

 an inch or more in length, producing a penicillate brush propor- 

 tionally as long as that of some species of Tamias or even Sciurus. 

 With this singular character others of equal tangibility are 

 coordinated. The description to be given will include some points 

 common to the genus, as, with one exception, the present is the 

 only species of Perognathus of which I have specimens in the flesh. 



The head is about one-third of the total length of head and 

 body ; broad and full across the temporal and orbital regions, 

 thence tapering rapidly to the produced but rather blunt snout. 

 The muzzle is entirely and densely pilous excepting a small nasal 

 pad, with a median furrow; the nostrils are very small and 

 irregular in contour. The long upper lip is heavily clothed with 

 stillish hairs, forming a fringe which droops over and hides the 

 incisors. The whiskers are numerous and very fine; besides the 

 labial set, the longest of which much exceed the head in length, 



