Reimeria ovata (Hust.) Levkov & Ector was found during field research conducted from 2013 to 2015 on the Wołosaty stream and its selected tributaries. Valves measured in the studied material are narrower than valves described in the currently available literature and have more striae per 10 µm. Specimens of R. ovata observed under a light microscope were morphologically very similar to those of R. sinuata, particularly in the case of small individuals. The precise distinction between these two species was only possible under SEM. R. ovata has been found in cold, oligotrophic waters, highly saturated with oxygen, with alkaline or circumneutral pH, but never in large numbers. The aim of this work was to identify the new locations of R. ovata and to determine morphological and ecological characteristics of this species.
