"^^"4^] ALLEN — MAMMALS 61 



Description. — The type (in early summer) still retains on the lower part 

 of the back a portion of the long winter pelage. The general color above 

 is buffy, largely mixed on the head with blackish, becoming clearer posteri- 

 orly and at the sides. The individual hairs are slaty for their basal three 

 quarters, with 'pale buff' tips; mixed with these are wholly blackish hairs 

 in the dorsal area, but these disappear at the sides, and the buffy tips 

 become more ochraceous, so that the sides of the neck and body and the 

 ventral surfaces, as well, arc ochraceous, with slaty bases to the hairs, 

 except on the chin and throat, the anal region, and the forearms, where the 

 hairs are white to their bases. The tail is ' pale buff ' above, slightly paler 

 below. The small round ears are quite concealed in the fur. The feet 

 are silvery with a dusky tinge. 



A second specimen, without skull, taken at Nijni Kolymsk, October 

 31, 1911, is in full winter pelage, some 24 mm. long on the rump. In color 

 it is nearly uniform ochraceous buff above and below, slightly deeper on 

 the rump, and paler on the belly. The dorsal region from the end of the 

 muzzle to the middle of the back is daikened by a considerable admixture 

 of black hairs wliich disappear posteriorly. The throat is nearly white, 

 and the forearms and hind legs below are pale buffy. 



Skull and teeth. — The skull does not differ remarkably from that of L. 

 obensis or L. lemmus, though nearly a fifth smaller than that of obensis and 

 slightly smaller than in lemmus. The palate is produced medially to form 

 a well-marked sharp process, instead of being blunt as in L. lemmus. The 

 incisive foramina are strongly and abruptly contracted behind. The 

 incisor teeth are nearly milk-white with a faint buffy tinge, instead of the 

 clear yellow of L. lemmus, and the third upper molar differs from that of 

 the latter in having the enamel walls of the prisms nearly straight instead 

 of curved, and the prisms themselves slope antero-internally instead of 

 being nearly transverse. 



Measurements. — The type was measured by the collector, as follows: 

 total length, 125 mm.; tail, 16; hind foot, 17.5. The second specimen 

 measured 117, 17, and 19 for the corresponding dimensions. The ear, 

 dried, measures 7 and 6.2 mm. in the two animals, respectively. 



The skull of the type measures: condylobasal length, 29.5 mm.; palatal 

 length, 17; diastema, 9.1; zygomatic breadth, 20.2; mastoid breadth, 

 15.5; interorbital constriction, 3.8; nasals, 8.8; maxillary tooth-row, 8.2; 

 mandibular tooth-row, 7.5. 



Remarks. — The discovery of this small lemming is one of the 

 important results of the expedition. It is remarkable for the 

 uniform coloration of both summer and winter pelages, the white 

 incisors, and the compressed enamel walls of the third upper molar. 

 It does not closely resemble L. lemmus nor the large L. obensis. 



