Phylum: Charophyta   Family: Desmidiaceae

Cosmarium eichlerianum (R.L. Grönblad) E.A. Messikommer 1957

A medium-sized desmid with semicells somewhat hexagonal in shape, the sinuses closed for the most part, lower part of sides convex, upper part concave giving emphasis to the truncate apex. Chloroplast axile with one pyrenoid.
Cell dimensions: L: 27.6-29.7 µm, B: 22.5-23.3 µm, Is: 7.8-8.7 µm; Th: 14.8-17 µm, L/B: 1.23-1.30.
Found in slightly acidic waters such as moorland pools, bogs and abandoned peat-cuttings. Its status in the Outer Hebrides is unclear, but as of 2025 it has rarely been recorded.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium. Part 1: Text. Part 2: Plates.