Re-examination of the type materials of Navicula exilis and Navicula cryptocephala (Naviculaceae, Bacillariophyceae)

Type material of Navicula exilis and Navicula cryptocephala from the Kutzing collection at the Natural History Museum, London, was re-investigated in light and electron microscopy. The morphology of these species was studied in detail using original materials and the nomenclature and previous studies of type material summarized. Navicula exilis is compared with Navicula cryptocephala, Navicula cryptocephala var. exilis, Navicula lothargeitleri and Navicula adversa.