XXVI.—Staurastrum paradoxum Meyen and S. gracile Ralfs in the British Freshwater Plankton, and a Revision of the S. anatinum-group of Radiate Desmids

Abstract

SynopsisAn attempt has been made to determine the identity of two desmids commonly recorded from the plankton of British lakes, Staurastrum paradoxum and S. gracile. The original descriptions of these species were clearly inadequate and many subsequent investigators have given their own interpretation as to their identity, so that from the British plankton alone at least six well-defined taxa have been referred to as S. paradoxum and four as S. gracile. Owing to this confusion, and in the absence of type material, it is suggested that the species S. paradoxum cannot be maintained. On the other hand, type material of S. gracile exists in the British Museum and has been re-examined. The principal characters of this species are described and figured and a list of synonyms given. In addition, those Staurastrum species and varieties frequently misnamed paradoxum or gracile, have been described in detail.