Cymbella rumrichiae

Valves are lanceolate to linear-lanceolate and dorsiventral with broadly rounded to rostrate apices. The dorsal margin is moderately arched; the ventral margin is weakly convex to nearly flat. The axial area is narrow. A central area is not evident on some specimens; on others it is small and rhombic. The raphe is lateral, becoming reverse-lateral near the proximal ends. Proximal raphe ends are deflected ventrally. Terminal raphe ends are deflected dorsally at 45 degrees. Striae are weakly radiate near the valve center, becoming strongly radiate near the apices. Areolae number 24-28 in 10 µm. One to five central stigmata may be present at the ends of the middle striae on the ventral side.

The specimens observed and presented here have a size range comparable to that of the type population from South America, as described by Krammer (2002). The larger specimens here, however, are not of the same shape as those in the original description. Further work is needed to clarify the relationship of the North American populations to the South American ones.