Cymbella stigmaphora

Valves are dorsiventral and rhombic-lanceolate with acutely rounded apices. The dorsal margin is strongly arched; the ventral margin is weakly convex with a tumid center. The axial is relatively wide. The central area is a somewhat wider than the axial area. The raphe is distinctly lateral. The raphe is weakly lateral, with ventrally deflected proximal raphe ends. The proximal raphe teminates with slightly inflated pores. Distal raphe fissures are deflected dorsally. Striae are radiate, becoming more strongly radiate near the valve apices. Areolae are distinct in LM and number 22-26 in 10 µm. A stigma is absent.

Note that using the optics of the time, Østrup (1910) perceived a single isolated stigma on the ventral side of the central nodule, hence the name stigmaphora or “stigma-bearing”. Using modern optics, Krammer (2002) was not able confirm the presence of a stigma on the type specimens, nor has a stigma been found in any of the other populations that have been examined.