Phylum: Charophyta   Family: Desmidiaceae

Staurastrum simonyi A. Heimerl 1891

A variable species as noted and illustrated by Kouwets (1988: 303, pl. 5: 1-12).
Overall cell dimensions: L: 18-28 µm; B: 20-30 µm; Is: 5.5-7.5 µm.
West, West & Carter (1923: 46) give the distribution for Scotland as “General, but scarce.” This is the current situation for the Outer Hebrides. Found in acidic moorland pools and peat bogs, often in benthic debris.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Kouwets, F.A.C. (1988). Remarkable forms in the desmid flora of a small mountain bog in the French Jura.
Van Westen, M.C. (2024). Sieralgen in Drenthe.
West, W., West, G.S. & Carter, N. (1923). A Monograph of the British Desmidiaceae, Volume 5.