Cymbopleura heinii has large broadly elliptic-lanceolate valves with rostrate apices. Areolae are coarse and number 16-18 in 10 µm. Proximal raphe ends are reverse lateral, with small ventrally deflected hooks. The hooks may or may not be evident depending on angle of view and depth of focus. Faint, surface spots are sometimes present in the axial and central areas.