Valves linear-lanceolate, lanceolate or lanceolate-elliptic, valve ends sometimes slightly protracted. Frustules form ribbon-like colonies.
Isopolar, bilaterally symmetrical.
Stria parallel to radiate, placed opposite each other, with round areola openings.
Spines on the virgae at the valve face/mantle junction can be present or missing.
A very small axial area can be present or missing.
Virgae are thickened internally.
A group of porelli form two small apical pore fields, or they are reduced or missing.
The cingulum consists of 3-4 open girdle bands and a large valvocopula.