Phylum: Charophyta   Family: Desmidiaceae

Cosmarium scenedesmus G.B. Delponte 1877

Until recently, this taxon was known as Cosmarium depressum (C.W. von Nägeli) P.M. Lundell 1871. (ICN illegal – name already taken). It is now considered synonymous with C. scenedesmus, which has priority. The main confusion species is Staurodesmus convergens, where the spines have not yet developed.
Cell dimensions: L: 36-44 µm, B: 37-45 µm, Is. 11-13 µm; Th. 19-20 µm L/B: 0.95-1.03.
Frequently found in circumneutral waters such as lochs, moorland pools and abandoned peat-cuttings.

References: 
Delponte, G.B. (1877). Specimen Desmidiacearum subalpinarum.
Kouwets, F.A.C. (in manuscript). European Flora of the Desmid Genus Cosmarium.
Van Westen, M.C. (2024). Sieralgen in Drenthe.