The eastern boundary of the range of the freshwater snail Stagnicola (Corvusiana) corvus has been clarified. The species was found in the State Nature Reserve «Prisurskiy» (Lake Buymas, floodplain of the River Sura). Previously, S. Corvus was registered from the River Oka basin (Moscow Region), and it was considered as the easternmost area of its distribution. The morphometric characterisation of S. Corvus, some features of its ecology as well as the diagnostic characters are given.