The species of Tolypella (A. Braun) A. Braun was found for the first time from Republic of Buryatia (Lake Baikal basin). The locality of T. prolifera (A. Braun) Leonh. is timed to the little reservoir in the upper part of Selenga River delta. The species was found in the multispecies cenosis with flowering aquatic plants and macroscopic algae in July 2012. A few small thalli were etiolated. The studied samples have no morphological difference from diagnosis. Presently, this locality of T. prolifera is the most eastern in Northern Eurasia. The new finding in Buryatia allowed to spread northeast limits area of this rare species. The specimens and biotope descriptions are given and several aspects of geography, ecology, biology and sozology are discussed. It is need to special attention to populations status and monitoring in considered region.