Phylum: Charophyta   Family: Desmidiaceae

Cosmarium pyramidatum L.A. de Brébisson ex J. Ralfs 1848

First described by Brébisson in Ralfs (1848: 94, pl. 15: 4) and illustrated by Jenner. There is a considerable size range with this species, which may involve more than one species.
Cell dimensions: L: 73-89 µm; B: 51-60 µm; Is: 17-22 µm; Th: 33-37; L/B: 1.37-1.50.
Common in peaty pools and bogs, also in rocky pools and lochs.

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.
Ralfs, J. (1848). The British Desmidieae.
West, W. & West, G.S. (1905). A Monograph of the British Desmidiaceae, Volume 2.