Cymbella cymbiformis

Valves are lanceolate and dorsiventral with bluntly rounded apices. The dorsal margin is moderately arched; the ventral margin is weakly concave with a slightly gibbous middle. The axial area is linear. The central area is small and elliptic, somewhat wider on the ventral side. The raphe is distinctly lateral, becoming reverse-lateral near the proximal ends. Proximal raphe ends are deflected ventrally and terminate with inflated pores. Terminal raphe fissures are deflected ventrally at about 45 degrees. Striae are widely spaced and nearly parallel at the valve center, becoming radiate near the apices. Areolae are distinct in LM and widely spaced, numbering 14-17 in 10 µm. Stigmata are variable in number. Usually there are 1 or 2 on the ventral side of the central nodule.

Note that the width of the specimens illustrated here not conform with the width of European C. cymbiformis (Krammer 2002). Further work may show this North American taxon to be a different species.