Description: The cells are a little longer than wide and wide, elliptical in shape. The longitudinal cell sides and the cell terminanations are rounded broadly elliptical. The central cut is deep and strongly extended towards the periphery. The cell wall is occupied with verrucae standing in vertical rows and offset from each other. Between the nipples there are little pores arranged in hexagonal patterns. In the chromatophores there are 2 pyrenoides per cell half.

Dimension: Length 60–70 µm, width 50–60 µm.

Occurrence: Occasionally in fens, alpine ponds and siltation zones of mountain lakes in mountainous areas up to 2600 m altitude, apparently absent in the lowlands.

Note: Primarily it could be confused with the very similar Cosmarium reniforme, whose cells are, however, more compact (only about 1.04-1.07 times longer than wide) and the sides are more flatly curved when viewed from the top.

Left: Original graphic by Prof. Lenzenweger.
Right: Photomicrograph by Prof. Lenzenweger. For microphotography, the microscope illumination was adjusted in such a way that as many features as possible that are important for species identification are prominently displayed.

Copyright by Prof. Rupert Lenzenweger, Ried im Innkreis, Austria.