The identity of Gomphonema clavatum Ehrenberg (Bacillariophyceae) and typification of five species of the genus Gomphonema described by C.G. Ehrenberg

This paper reports on investigations of original material of C.G. Ehrenberg housed in the Museum fur Naturkunde, Berlin (BHUPM). The type material of eight Gomphonema species described by Ehrenberg was studied. The following species are lectotypified: G. clavatum Ehrenberg, G. longiceps Ehrenberg, G. longicolle Ehrenberg, G. mustela Ehrenberg and G. rhombeum Ehrenberg. The holotype of G. tenuicolle Ehrenberg is illustrated. In addition, the original material of G. leibleinii Agardh, housed in the Museum of Natural History, Vienna, was studied. The most important results are: G. clavatum and G. leibleinii are determined to be conspecific with G. olivaceum (Hornemann) Brebisson, G. longiceps is the correct name of G. clavatum sensu Krammer & Lange-Bertalot (1986.) pro parte, and G. mustela represents a (post) initial valve of G. coronatum Ehrenberg. Some of the problems and difficulties that may arise when working on Ehrenberg's material or types are discussed with special reference to G. americanum and G. turris.