Phylum: Charophyta   Family: Desmidiaceae

Staurastrum anatinum var. subanatinum (W. & G.S.West) P.F.M. Coesel & K.J. Meesters 2013

First described and illustrated by West & West (1902: 54, pl. 1: 28) As St. vestitum var. subanatinum. Much later it was move by Coesel & Meesters (2013: 63, pl. 85: 1-3) as a variety of St. anatinum. It differs from the nominate variety in having two prominent bifurcate spines projecting from the middle of each margin, as seen in apical view.
Cell dimensions: L: 35 µm; B: 70-102 µm; Is: 12-13.5 µm.
Found in the plankton of the larger lochs, often at altitude. Infrequently encountered in the Outer Hebrides.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus.
West, W. & West, G.S. (1902) A contribution to the freshwater algae of the north of Ireland.