Phylum: Chatophyta   Family: Desmidiaceae

Staurastrum oxyacanthum var. polyacanthum C.F.O. Nordstedt 1885

First described and illustrated by Nordstedt (1885: 11, pl. 7: 9). Both the nominate and this variety are quite rare in Britain with most records coming from the west-coast regions.
Cell dimensions: L: 40-48 µm; B: 50-65 µm; Is: 11-13 µm.
Found in marginal vegetation of lochs and moorland pools, also bogs.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Nordstedt, C.F.O. (1885). Desmidieer samlade af Sv. Berggren under Nordenskiöld'ska expeditionen till Grönland 1870.
West, W., West, G.S. & Carter, N. (1923). A Monograph of the British Desmidiaceae, Volume 5.