Planothidium frequentissimum var. magnum (F.Straub) Lange-Bert.
Planothidium frequentissimum var. magnum in Iconogr. Diatomol. 6: 276. 19991
is new combination for Achnanthes rostrata var. magna
Planothidium frequentissimum var. magnum
1. (Basionym:) fig. 10: 142, 11: 142b