A taxonomic reappraisal of someStephanodiscusspecies (Bacillariophyta)

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Abstract
The following species are examined: Cyclotella minutula Kützing, Stephanodiscus minutus H. L. Smith Type 504, Grunow in Cleve & Möller 221, S. oregoniae H. L. Smith Type 506, Discoplea oregonica Ehrenberg, Stephanodiscus carconensis Grunow var. carconensis, S. carconensis var. minor Grunow, and S. carconensis var. pusillus Grunow. The study is based on original material, drawings, and annotations from collections or exsiccata of Kützing, Ehrenberg, H. L. Smith, Cleve & Möller, and Möller, and where possible also on light and electron microscope studies of unmounted type material. The results show both morphological differences and similarities between the observed species. The material on slides 504 (H. L. Smith) and 221 (Cleve et Möller) are identical. The material on slide 506 (H. L. Smith, Klamath Lake) is identical with that from the Grunow collection (slide 2007, Klamath Lake). The name Stephanodiscus minutus has never been validly published, and has been widely misused, but the diatom to which it was given is distinct. This taxon is herewith validly described as S. medius Håkansson. The name Stephanodiscus oregoniae on slide 506 (H. L. Smith) has never been validly published, but is synonymous with the validly published S. carconensis var. minor and S. carconensis var. pusillus. Discoplea oregonica is transferred to the genus Stephanodiscus and a lectotype is chosen.