Frustules rectangular in girdle view forming linear, ribbon-like colonies. Valves linear, lanceolate or elliptical with rostrate to capitate ends.
The sternum is narrow or absent.
Striae uniseriate and extending onto the mantle, areolae occluded by simple vela.
Apical pore fields are present.
A single rimoportula is present near one valve end.
Spines on the valve margins are either simple projections or complex with large interdigitating, spatulate tips.
The cingulum consists of 4-6 open, ligulate copulae, each with a single row of poroids.
Multiple disc-shaped plastids are present.