FOUR NEW GENERA BASED ON<i>ACHNANTHES</i>(<i>ACHNANTHIDIUM</i>) TOGETHER WITH A RE-DEFINITION OF<i>ACHNANTHIDIUM</i>

Abstract

The genus Achnanthidium comprises a collection of monoraphid species common in freshwaters and less so in marine habitats, though the latter are relatively uninvestigated as far as this genus is concerned. We propose that Achnanthidium be confined to the taxa around A. minutissima. Some of the remaining taxa are transferred to four new genera, Planothidium, Rossithidium, Karayevia and Kolbesia. This still leaves a large number of species to be re-allocated and these, for the moment, will have to be left as Achnanthidium sensu lato.