Frustulia creuzburgensis

Valves with slightly rostrate, rounded apices, 26.0 - 38.0 µm in length by 6.0 - 8.0 µm in breadth. Valve mantle of moderate depth. The two raphe branches are arched along their entire length, resulting in asymmetrical valve face ornamentation. The distal raphe ends begin more or less centered along the longitudinal axis, and the raphe curves unilaterally toward the dorsal margin as it approaches the central area. The external proximal raphe ends are deflected in the same direction as the curve of the raphe branches. Enlarged poroids occur near the external distal raphe ends, positioned within a transverse depression. Striae are composed of rows of round, although commonly elongate, areolae. Areolae are internally occluded. The valvocopula is closed, and includes a row of projections on the internal side and a rough external notch near the center of the band. The notch is of varying size and shape and exposes a series of alternating poroids and small protuberances. In addition to the valvocopula, four open copulae are present, each with two rows of poroids.