The original (type) materials of Synedra flexuosa Br eacute;b. ex K uuml;tz., Synedra biceps W.Sm., and Eunotia flexuosa var. bicapitata Grunow conserved at the Van Heurck Collection (BR, Meise gated using light and scanning electron microscopy. All three names refer to the same species: Eunotia flexuosa (Br eacute;b. ex K uuml;tz.) K uuml;tz.. The present contribution unravels the taxonomic history of Eunotia flexuosa. Observations of the three taxa indicates that they are identical in their morphology, making Synedra biceps and Eunotia flexuosa var. bicapitata younger synonyms of E. flexuosa. The species is characterised by its very long, slightly arcuate to almost linear valves with more or less parallel valve margins, not (or slightly) tapering towards the inflated apices and terminal raphe fissures recurving onto the valve face.