Revision of the brackish-freshwater diatom genus Bacillaria Gmelin (Bacillariophyta) with the description of a new variety and two new species

Bacillaria paxillifera - perhaps better known by its synonym B. paradoxa - is epi-typified with material from close to the type locality. Its morphology - from the living cell and intact colony to the fine structure of the valve and girdle bands - is established using light microscopy, transmission electron microscopy and scanning electron microscopy. Since B. paxillifera is also the generitype, Bacillaria is here revised and emended to include only brackish-freshwater taxa showing the unique fibulate raphe system and construction type of this genus. Three new taxa are described within the re-defined genus: B. paxillifera var. czarneckii, B. kuseliae and B. urve-millerae, differing mainly in their raphe flanges, cell-outline and shape and number of plastids. The first taxon was found in both the Mississippi River, USA, and the River Weser, Germany, the second in the Avon River, Australia, and the third at a freshwater influx into the Atlantic in The Gambia, West Africa. Historical taxa, such as Grunow's B. paxillifera var. tumidula, var. tropica, and var. pacifica were also studied and lectotypified.