Abstract
Six species of Adlafia Moser, Lange-Bertalot et Metzeltin from Brazilian freshwater environments were investigated under light and electron microscopes. Two new taxa are described. Adlafia decora Tusset, Tremarin & T. Ludwig is characterized mainly by linear-lanceolate valves and rostrate ends, and A. triundulata Tusset, Tremarin & T. Ludwig shows triundulate linear valves contour and subcapitate apices.