Abstract
Staurophora brantii is described from streams of the northwestern Great Plains in the western United States. The new species is placed in Staurophora by virtue of its plastid type, valve structure, and ecology. It is distinguished from similar species by its size, valve shape, end shape, striae count, and habitat. Staurophora brantii sp. nov. lives in alkaline freshwater streams with soft, muddy bottoms and elevated concentrations of electrolytes, particularly sodium and sulfate. Stauroneis tackei, an associate of Staurophora brantii on the Great Plains, is transferred to Staurophora.