Planothidium biporomum (M.H.Hohn & Hellerman) Lange-Bert. Planothidium biporomum (M.H.Hohn & Hellerman) Lange-Bert. in Iconogr. Diatomol. 6: 275. 19991is new combination for Achnanthes biporoma M.H.Hohn & Hellerman1. (Basionym:) fig. 2: 5-6