LEMMUS 203 



Range. — New Siberian Archipelago. 



Characters. — Summer jjelage like that of the typical sub- 

 species, but ears more rusty yellow and sharply contrasted with 

 the colour of the head ; brownish colour of top of head extending 

 to the lips. In winter with a superficial resemblance to winter 

 specimens of Dicrostonyx, the fur almost white, the claws greatly 

 enlarged (but not bifurcate), blunt, with enlarged horny ungual 

 pads. Fur in winter very long and silky, light " pinkish 

 buff," greyer on the back, paler {"' cartridge buff ") on the 

 beUy. 



Skull compared with that of L. o. ohensis with shorter nasals, 

 which do not completely cover the nasal aperture in the dorsal 

 view. Zygomatic arches less widely spreading. Interorbital 

 crest in fully adult specimens very low or absent. Braincase 

 large, nearly smooth and rounded even in quite adult specimens. 

 Interparietal about half as long as wide. Auditory bullae larger. 

 Upper incisors more projecting; cheek-teeth heavier. 



For external and cranial measurements, see tables at end of 

 volume. 



Ronarhs. — Vinogradov says that the peculiar characters of 

 this interesting form almost entitle it to specific rank ; but some 

 of the specimens have the characters less sharply developed, 

 and his L. o. hungei inhabiting the region around the mouth 

 of the Lena is in some respects intermediate between L. o. ohensis 

 and L. o. novosibirieus. The superficial resemblance of the latter 

 in winter to Dicrostonyx is no doubt, as Vinogradov suggests, a 

 case of convergent or rather parallel evolution between two forms 

 living under the same severe climatic conditions on the far 

 northern border of Siberia. 



2c. Leininus obensis chrysogaster Allen. 

 1903. Lemmus obensis chrysogaster Allen, Bull. Amer. Mus. N.H., 19, 

 p. 153. 



Type. — American Museum N.H., No. 18762 ; young specimen, 

 skin and skull, collected July 1901 by N. G. Buxton of the Jessup 

 North Pacific Expedition. 



Type locality. — Gichiga, west coast of Okhotsk Sea. 



Characters. — Colour (in dried out spirit specimen) yellowish- 

 brown above varied with black, more greyish-brown and less 

 yellowish on the head and neck, the fulvous tint gradually 

 increasing in brightness and amount from the shoulders pos- 

 teriorly, becoming strong yellowish-rufous on the lower back 

 and rump ; sides and ventral surface orange ochraceous, paler 

 on the throat and at base of tail ; chin and sides of mouth soiled 

 buffy white ; top of nose pale dusky brown, passing posteriorly 

 into the dull yellowish grey-brown of the upper surface of head. 

 ;Feet dusky greyish-brown; claws dusky horn-colour. Ears 

 ivery small, orbicular, wholly concealed. Tail very short, dusky 



