Abstract
Achnanthidium Kützing is considered a monoraphid diatom genus due to its heterovalvar frustule with one raphid and other araphid valve; also, is characterized by the linear, lanceolate or elliptical valves, with girdle view forming a deep V. In São Paulo State is estimated that around 22 species/varieties of the genus are known. However, most of the information has not been published and …