Phylum: Charophyta   Family: Desmidiaceae

Staurodesmus omearae (W. Archer) E. Teiling 1948

First described and illustrated by Archer (1858: 254, pl. 21: 8-13) as Staurastrum omearae. It was later moved to its current genus by Teiling (1948: 254, pl. 21: 8-13). This is morphologically a quite variable taxon. West, West & Carter (1923: 13, pl. 132: 6) depict a zygospore of small size with numerous fine spines, attributed to Archer. This must belong to a different species because the true zygospore is larger with 7 to 8 robust spines, as seen in face view.
Cell dimensions: L: 15-21 µm; B: 14-21 µm; Is: 5-9.2 µm; Sp: 5-15 µm; Overall LxB: 22-35 x 24-41.
Zygospore dimensions: core: 20-21 µm; spines: 11-12 µm; overall: 41 µm.
A fairly common taxon, found in slightly acidic conditions such as the larger lochs and shallow moorland pools.

References: 
Archer, W. (1858). Supplementary catalogue of Desmidiaceae found in the neighbourhood of Dublin with description and figures of a proposed new genus and of four new species.
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Teiling, E. (1948). Staurodesmus, genus novum. Containing monospinous Desmids.
Van Westen, M. (2024). Sieralgen in Drenthe.
West, W., West, G.S. & Carter, N. (1923). A Monograph of the British Desmidiaceae, Volume 5.