SAOCOMYID/E— PEROUNATHIDIN^— P. FAS01 ATITS. 50 1 



or more; tailless; hind fool about one inch. Tail decidedly shorter than 

 head and body, not penieillate. Ears large; antitragus distinctly lobed. 

 Holes naked to the heels, — at least along a median strip. Above, reddish-yel- 

 low, closely lined with blackish ; below, including fore leg all around, white; 

 these two colors separated by a conspicuous stripe of lawn-color or salinon- 

 red running the whole length of the body ; tail distinctly bicolor. 



Habitat. — United States, west of the Mississippi and east of the Rocky 

 Mountains, and northern portions of Mexico. (Originally described from the 

 month of the Yellowstone; redescribed from Chihuahua. Specimens exam- 

 ined by me from Nebraska, Kansas, Texas, and Chihuahua.) 



I regret that the material before me includes no specimens in the flesh, 

 since I am thereby prevented from giving the size and form of the species 

 with desirable precision; fortunately, however, in this instance the characters 

 of the species are so strongly marked that lack of elaborate details of form 

 will result in no misunderstanding. The coloration, alone distinctive, can be 

 accurately given from several well-prepared skins before me. 



This species, the type of the genus, exhibits very distinctly the two lead- 

 ing features of external anatomy which distinguish Pe/ognalhus proper from 

 Cricetodipus ; namely, the lobe of the antitragus and the naked strip of the 

 sole extending cpiite to the heel. It is much the largest species of the genus 

 known to inhabit the United States, considerably exceeding P. penicillatus 

 (which about equals Hesperomys leucopus in size), and, in fact, some speci- 

 mens are little if any smaller than Tamias quadrivittatus. For the reason 

 above given, the dimensions cannot be stated with precision; but the length 

 from nose to root of tail is obviously more than four inches in all but one of 

 the specimens before me; the tail is decidedly shorter than the head and 

 body (in all the other species treated in this paper it is as long or longer). 

 The vertebrae of the tail of the only specimen before me in which these 

 bones remain in situ measure less than 4.00 inches, the length of the head 

 and body of the same specimen being about 4.50. Likewise, the hind feet 

 are proportionally shorter than in any of the other species ; they average only 

 one inch in length, thus not exceeding those of P. penicillatus, winch is a 

 smaller animal. On the contrary, the ears are larger, both absolutely and 

 relatively, than those of any other species, standing about 0.40 high, meas- 

 ured from the notch; the ears thus project conspicuously above the fur of 

 the parts; the flap is suborbicular in outline; the antitragus develops a very 



