Frustules isovalvar, bilaterally symmetrical, naviculoid.
Raphe located on prominent sternum, sternum constricted on one side at centre. Proximal raphe ends straight or slightly deflected to one side, terminal raphe fissures curved to the opposite side.
Axial area formed by two longitudinal depressions located on each side of the sternum; depressions contain transversally orientated microcostae. Conopeum absent.
Stria uniseriate, separated by hyaline area from row of mantle areolae.
Two lateral chloroplasts mostly adjacent to cingulum on each side of the valve.