Phylum: Charophyta   Family: Desmidiaceae

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

First described and illustrated by West & West (1902: 53, pl. 1: 20) as Staurastrum latiusculum. It was later moved by Coesel & Meesters (2013: 82, pl. 114: 5-6) as a variety of S. chavesii. The only difference is a spine at the base of the processes.
Cell dimensions: L: 14-20 µm; B: 18-27 µm; Is: 8-9 µm.
Both the nominate and this variety are very rare, the latter only known previously from Ireland. The habitat is acidic oligotrophic moorland bogs and pools, also associated with Sphagnum.

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.