Shells and opercula of an aquatic snail Bithynia tentaculata (L.) occur commonly in Quaternary deposits as a substantial component of subfossil malacocenoses. They have been noted mainly in lacustrine chalk and calcareous gyttja, as well as in silts and muds accumulated in fluviatile environments. The contemporary geographical range of this taxon is very wide, comprising the whole Palaearctic except areas extending north of the Arctic Circle. In subfossil assemblages of molluscs B. tentaculata (L.) has been described almost exclusively from Holocene and Interglacial deposits, apart from a few localities of sediments accumulated during the cold periods of Pleistocene, particularly in Late Glacial phases. As the range of the mentioned species is limited to the zones of the temperate, boreal and Mediterranean climate, it can be pointed out as a climatic- stratigraphic indicator, useful in malacological analysis of Quaternary deposits. Only a few taxa of aquatic molluscs have such a value. The proportion of shells and opercula characterizes sedimentary environments.