Cymbella mexicana var. kamtschatica

Valves are relatively broad, cymbelloid and semi-elliptic. Apices are bluntly rounded and weakly protracted. The dorsal margin is strongly arched; the ventral margin is slightly convex to nearly flat. The axial area is linear and a bit wider than the raphe. The central area is small and circular to elliptic in shape. A single large stigma is present between the proximal raphe ends. The raphe branches are lateral, becoming narrower near the proximal and distal ends. Proximal raphe ends terminate in bulbous central pores that are deflected slightly towards the ventral margin. Terminal raphe fissures are deflected dorsally at about 45º. Well developed porefields are present at both apices. Striae are radiate throughout. The dorsal and ventral striae in the central portion of the valve are variable in length. Areolae are very distinct in LM and number 10-12 in 10 µm. Areolae on the ventral side of the central area are elongate and triangular in shape.

This is a smaller, more compact form of C. mexicana with bluntly rounded and weakly protracted apices. It may occur in association with the nominate variety, but it is often the only variety of the species that is present.

Editor's note: Users should be aware that this variety may represent small forms of the nominate species. We appreciate documentation and feedback on the occurrence of this taxon in North America.