Transfer of Achnanthes decipiens to the genus Nupela

Achnanthes decipiens Reimer was described from a benthic sample collected from a small stream in South Carolina, USA. Examination of the type material with light and electron microscopy showed that this species belongs to the genus Nupela Vyverman & Compere to which it is transferred. Nupela decipiens (Reimer) Potapova is similar to N. praecipua (Reichardt) Reichardt by the size and shape of the valve and the striation pattern, but differs from it by the large central area on the raphe valve. So far, N. decipiens has been reported from a few slightly acid soft-water streams in eastern North America.