Studies on type material from Kützing’s diatom collection VIII. Species assigned to the genera Epithemia Brébisson ex Kützing and Rhopalodia O. Müller

We detail the diatom taxa described by F.T. Kützing across three of his publications that have been referred to the diatom genera Epithemia and Rhopalodia. Taxa considered include Frustulia adnata, F. picta, E. alpestris, E. musculus, E. porcellus, E. proboscidea, E. sorex, E. ventricosa, E. vertagus, E. ventricosa β. gregaria and E. reticulata. For these 12 taxa, this represents the first time Kützing’s specimens have been illustrated with light microscopy. Most of the material consulted here is from the Natural History Museum, London, though we also reviewed material from the Academy of Natural Sciences for E. adnata. We present light microscope images of the Kützing taxa and complement these observations with images of the type slides, material packets and both herbarium (unpublished) and published drawings. In some cases, modern concepts of Kützing species are supported, but in others it is likely that species concepts will be changed by the specimens in the type material. Lectotypes are designated for Epithemia adnata and Epithemia reticulata.