Phylum: Charophyta Family: Desmidiaceae
Staurastrum arcuatum var. subavicula (West) Coesel & Meesters 2013
A tychoplanktonic species described as common on the continent. It is proving to be scarce in the Outer Hebrides. Coesel & Meesters (2013) describe the semicells as ellipsoid with relatively shorter processes than the nominate variety. However, the cell-shape is quite variable.
References:
West, W. & West, G.S. (1894) New British freshwater algae.
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus.