Cymbopleura incerta

Valves are lanceolate and moderately dorsiventral with rounded apices. Except for the largest valves, where dorsal and ventral margins are equally arched, the dorsal margin is much more strongly arched than the ventral margin. In small specimens, the ventral margin may be flat, or even slightly concave. The axial area is narrow, widening gradually toward the ellliptic central area, which is from 1/3 to 1/2 the width of the valve. The axial and central areas form a narrow longitudinal lanceolate space that is displaced somewhat to the ventral side of the apical axis. The raphe is lateral, becoming reverse-lateral near the central valve. The proximal ends are slightly inflated and deflected toward the ventral side. The distal raphe fissures are narrow and hooked toward the dorsal side. Striae are slightly radiate, becoming more strongly radiate near the apices. Areolae in the striae number 28-32 in 10 µm.