MORPHOLOGY AND IDENTITY OF AULACOSEIRA ITALICA AND TYPIFICATION OF AULACOSEIRA (BACILLARIOPHYTA)

Abstract

Original material of Ehrenberg's from Santa Fiora (Tuscany, Italy) was examined to establish the identity of the diatom to which Ehrenberg gave the name Gaillonella italica. It was compared with other Ehrenberg material, notably from New England, and with numerous other samples, both fossil and recent, with a view to understanding the taxonomy of this species. Although Ehrenberg later discarded the name, it was validly published and we consider it synonymous with G. crenulata. However, despite the earlier publication of G. italica, G. crenulata remains the type of the name of the genus Aulacoseira. New observations on the rimoportulae and the velum together with recent illustrations of separation valves have been added to the features used to distinguish the species from others in the genus, of which, the most important, though hitherto neglected, is the curving of the pore rows to the left (sinistrorse). We draw attention to the fact that A. italica has often been confused with A. valida.

Key index words:

• Aulacoseira italica
• Aulacoseira crenulata
• Aulacoseira crenata
• Bacillariophyta
• morphology
• nomenclature
• systematics