Cells isovalvar, isopolar and bilaterally symmetrical.
Valves are elliptical to elongate in valve view, quadrate or rectangular in girdle view with broadly rounded, subrostrate, rostrate or capitate poles.
Cells joined either at the valve face to form ribbon-like colonies, or at one corner to form zig-zag or stellate colonies.
Striae are fine, uniseriate with small, round areolae; striae parallel and sometimes radiate towards poles.
Internally prominent transapical ribs extend from the sternum to the mantle.
Narrow axial area without central area.
Apical pore field present and a single, transapically orientated rimoportula close to the pore field.
Girdle bands with rows of pores.
Many small discoid, rod-like, or plate-like plastids.