Achnanthes rostrata var. magna F.Straub Achnanthes rostrata var. magna F.Straubis basionym for Planothidium frequentissimum var. magnum (F.Straub) Lange-Bert. in Iconogr. Diatomol. 6: 276. 199911. (Basionym:) fig. 10: 142, 11: 142b