Staurodesmus boergesenii is easy to overlook in fresh samples due to its small size. From a sample about 2 weeks old from the Schwemm Moor in Austria, I was able to isolate and examine several specimens more closely in June 2025.

Characteristic are the 4 short spines that arise almost horizontally at the corners of the flat apices, and the rather broad isthmus that only slightly separates the two semi-cells. The cell wall is smooth and without structure. In the cytoplasm there are some small granules, which are probably starch grains.

Staurodesmus boergesenii is easily confused with Staurodesmus crassus. Lenzenweger (1997) points out that Staurodesmus crassus has more strongly convex, arched apices. Since the apices in my population were almost flat, this must be Staurodesmus boergesenii.