Dicrostonyx torquatus (Pallas, 1778) . Nova Spec. Quad. Glir. Ord., p. 206.

TYPE LOCALITY: Siberia, mouth of River Ob .

DISTRIBUTION: Palearctic tundra from White Sea, W Russia, to Chukotski Peninsula, NE Siberia, and Kamchatka; including Novaya Zemlya and New Siberian islands, Arctic Ocean (see Corbet, 1978c).

SYNONYMS: chionopaes, lenae, lenensis, pallida, ungulatus .

COMMENTS: Chromosomal traits of populations from the Polar Urals (D. t. torquatus), the Laptev Sea coast and Rautan Island off the coast of the Chukotka Peninsula (D. f. chionopaes) are similar, and progeny of crosses between these two subspecies are fertile (Gileva, 1980). Unusual sex-chromosome constitution and other chromosomal information were summarized by Gileva et al. (1980), Gileva (1983), and Zima and Krâl (1984a). Once believed to encompass most or all New World populations (e.g., Rausch, 1953, 19636) but their level of relationship to D. torquatus proper is now unclear (see remarks under genus).