This paper is dedicated to the memory of Dr. Alexander Kafanov, promiment Russian malacologist and zoogeographer, who died in April 2007.
Abstract Gyraulus stroemi Westerlund, 1881 is a species distinct from G. acronicus (A. Férussac, 1807). It was, however, overlooked by the W-European malacologists for a long time. In this paper the shells as well as the anatomy have been
studied thoroughly (including syntypes of Planorbis stroemi) and compared with morphological and anatomical features of G. acronicus. By means of scanning of museum collections and the literature, a distribution map was constructed which
reveals that G. stroemi is a species that lives predominantly in the Artic and Subarctic.
‡In the Russian literature the genus name Gyraulus is mentioned as a subgenus of Anisus. The problem of subgrouping is not discussed here, so only the genus name Gyraulus is used in this paper for the sake of uniformity.