STUDIES ON THE DIATOM GENUS NAVICULA BORY. VII. THE IDENTITY AND TYPIFICATION OF NAVICULA GREGARIA DONKIN, N. CRYPTOCEPHALA KÜTZ. AND RELATED TAXA

Abstract

Morphological investigations of specimens of Navicula gregaria, N. cryptocephala, N. cryptocephala var. exilis, N. capitatoradiata, N. veneta and N. phyllepta were performed using light and electron microscopy. Both type and modem samples were examined. The typification of each taxon was reviewed; Patrick's typifications of N. cryptocephala and N. gregaria are supported, but the nomenclatural changes proposed by Lange-Bertalot are rejected. Based on Kiitzing's type material there is insufficient justification for recognising N. cryptocephala var. exilis as a discrete species but it is useful to retain the varietal distinction. Species descriptions (to aid identification by light microscopy) are given with the type localities and locations of type material. Illustrated standardization of descriptive terminology for valve shapes and endings is advocated.