Phylum: Charophyta   Family: Desmidiacea

Cosmarium triomphalum (R. Gutwinski) W. Schmidle 1898

Until recently, this species was described as C. dickii Coesel 1989, but it is identical to the species described by Schmidle in 1898 as C. triomphalum. This latter name therefore has priority. The main distinguishing character is the two supraisthmial granules. It also has a series of intramarginal granules.
Cell dimensions: L: 22-29 µm, B: 19-25 µm, Is: 6-9 µm; 12-15 µm, L/B: 1.05-1.22.
A reasonably common species found in the tychoplankton of circumneutral waters.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Kouwets, F.A.C. (in manuscript). European Flora of the Desmid Genus Cosmarium.
Schmidle, W. (1898). Über einige von Knut Bohlin in Pite Lappmark und Vesterbotten gesammelte Süsswasseralgen.
Van Westen, M. (2024). Sieralgen in Drenthe."