1903.] Allen, Mammals from Northeast Siberia. I 77 



Summer pelage. Above dark reddish brown, including the anterior 

 surface of the fore limbs to the carpus, and the outer surface of the 

 hind limbs to the base of the toes; ventral surface, inside of the limbs, 

 fore feet, and apical half of hind feet white, the ventral surface un- 

 mixed with any brown mottling; edge of upper lip and lower half of 

 cheeks white, like the ventral surface; ears very small, brown like the 

 dorsal surface; tail very short, much shorter than the hind foot, 

 wholly brown, uniform with the color of the back, the tip not dusky. 



Winter pelage. Wholly pure white, including the tip of the tail. 



Measurements. Type: Total length, 158 mm.; tail vertebrae, 16; 

 hind foot, 21. Skull, total length, 28.5; zygomatic breadth, 13.3; 

 mastoid breadth, 12.5. 



A second specimen in summer pelage from Marco va, with- 

 out measurements and skull imperfect (see Mr. Buxton's 

 notes below), is similar in coloration to the type, but slightly 

 larger and evidently a male. 



Besides the two specimens in summer pelage one from 

 Gichiga and one from Marcova, as already noted there are 

 two in winter pelage, in alcohol, collected by Mr. Jochelson at, 

 Verkhene Kolimsk, on the Kolyma River, in January, 1902.. 

 These are male and female, and measure as follows: Male: 

 Total length, 184 mm.; tail vertebrae, 19; hind foot, 23. Fe- 

 male: Total length, 166; tail vertebras, 13; hind foot, 19. 



The measurements given by Mr. Stone for Putorins rixosus 

 eskimo (Proc. Acad. Nat. Sci. Phila., 1900, p. 44) considerably 

 exceed those of P. pygm&us, being for two males, respectively,, 

 total length, 204 and 230; tail vertebras, 28 and 31 ; hind foot,. 

 20; while three females range from 178 to 184 in total length,, 

 tail 2225, an d hind foot 16-23. 



The much smaller size, the very short tail, and greatly 

 reduced ears distinguish this species at a glance from true 

 P. nivalis, as shown by a Swedish specimen now before me. 

 Its nearest ally and the only species with which it needs com- 

 parison is Putorius rixosus Bangs, from Arctic America (type 

 locality, Osier, Saskatchewan), from which it differs in being 

 much smaller, with the tail only half as long as in that species. 

 Mr. Stone's P. rixosus eskimo, from Point Barrow, Alaska, is 

 nearer the Siberian form, but differs from it in larger size and 

 in having the tail vertebrae loriger than the hind foot instead 



[March, 1903] 12 



