Cells solitary or in chains.
Cells cylindrical in girdle view, mostly circular in valve view. Valve face flat to concentrically undulate.
Fascicles radial extending onto mantle, separated by interfascicles, the latter can be raised and branched. Interfasciles thickened internally near valve margin, forming alveolar chambers.
External areola openings round or polygonal, internally areolae occluded by domed, perforated cribrae; cribrae flattened on valve mantle.
Conical separation spines present at valve face/mantle junction, linking spines can be present.
Marginal fultoportulae situated on mantle interfascicles, fultoportulae can be present in centre of valve face. Fultoportulae with simple, round external openings or short tube, internally with central tube and satellite pores.
Rimoportulae located on valve mantle. Girdle composed of several copulae.
Numerous small, peripheral chloroplasts.