Cymbella lanceolata

Valves are long and slender, dorsiventral and lanceolate with rounded apices. Length-to-width ratio ranges from 4.9 in smaller specimens to 7.8 in the largest specimens. The dorsal margin is moderately arched. The ventral margin is slightly concave with a gibbous center. The axial area is narrow and linear, slightly wider than the raphe. The central area is small and ovoid. The raphe is lateral, becoming filiform near the proximal and distal ends. Externally, the proximal raphe ends are strongly recurved toward the ventral side. Terminal raphe fissures are deflected dorsally at an angle of almost 90 degrees. Striae are radiate throughout, becoming more strongly radiate near the apices. Areolae number 10-14 in 10 µm. Some elongate, stigma-like areolae appear at the proximal ends of the median ventral striae, but otherwise stigmata are absent.

Note on the type: The original description of Frustulia lanceolata (Agardh 1827) did not include illustrations. Krammer (2002, p. 125) examined the type material from Carlsbad (Bohemia) and did not find any cymbelloid diatoms. Krammer designated a neotype from Westphalia, Germany. Images of the neotype specimens (Krammer 2002, plate 144, figs 1-5) are given below.