Small cells, frustules can form colonies, with cells connected at the valve face with spines or with mucilage pads at the edges of the valves.
Valves elliptical, linear or cruciform. Striae uniseriate, extending onto the mantle, with long, slit-like areolae containing finely branched occlusions.
One or two apical pore fields of variable size present at the apices. Rimoportula absent.
Spines simple, bifurcate or branched, situated on valve face/mantle junction between rows of areolae.
Mantle plaques often present.
Cingulum consisting of several plain, open and ligulate copulae with granulose abvalvar margins; valvocopula large, relative to copulae, each with fimbriate advalvar margin.