Valves dorsiventral with convex dorsal and concave ventral margin; frustules with many girdle bands, usually lying in gridle view, then mostly linear or rectangular.
Striae with complex areolae.
Eccentric raphe system, positioned along the ventral margin, biarcuate with each branch arched toward the dorsal margin. Externally proximal raphe endings slightly expanded, internally raphe slit more or less continuous.
Internally thicker and thinner transapical ribs.
Valvocopula with septum-like extensions.