Phylum: Charophyta   Family: Desmidiaceae

Staurastrum cornutum W. Archer 1881

First described by Archer (1881: 232) from Connemara, Ireland. Roy (1893: 180, pl. 4: 5) described his find in Aberdeenshire as Staurastrum cornigerum seemingly unaware of Archer's find. It is now synonymised. West, West & Carter (1923: 31) just replicate Roy’s data. An extremely rare Arctic-alpine species that was first recorded from the Outer Hebrides in 2022.
Cell dimensions: L. 34-50 µm, B. 40-57 µm, Is. 11-12 µm.
Found with submerged vegetation in meso-oligotrophic waters such as lochans and moorland pools.

References: 
Archer, W. (1881). Staurastrum nov. sp. In Proceedings of learned societies. Dublin Microscopical Club.
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Roy, J. (1893). On Scottish Desmidieae.
West, W., West, G.S. & Carter, N. (1923). A Monograph of the British Desmidiaceae, Volume 5.