Microtus obscurus (Eversmann, 1841) . Mem. Univ. Kazan, 156.

TYPE LOCALITY: Siberia, Altai Mtns .

DISTRIBUTION: Russia from the Crimea east through Siberia to the upper Yenesei River, south through NW Mongolia, NW China (Xinjiang), the Altai Mtns, Lake Balkash, to the Caucusus and N Iran (see Zagorodnyuk, 1991a).

SYNONYMS: brevirostris, gudauricus, ilaeus, ileos, innae, iphigeniae, macrocranius, transcaucasicus, transuralensis.

COMMENTS: Subgenus Microtus, arvalis species group sensu Zagorodnyuk (1990) . Formerly included in M. arvalis (e.g., Corbet, 1978c) but shown to be a distinct species by Zagorodnyuk (1991a, b) based on morphological and chromosomal features. The species appears to be parapatric with M. arvalis (Zagorodnyuk, 1991a) .