Phylum: Charophyta   Family: Desmidiaceae

Staurastrum pileolatum L.A. de Brébisson ex J. Ralfs 1848

First described by Brébisson in Ralfs (1848: 215, pl. 35: 22) and illustrated by Jenner. A predominantly triradiate species.
Cell dimensions: L: 35-45 µm; B: 19-25 µm; Is: 16-18 µm.
An upland species of acidic bogs, also from moss on wet rocks. Quite a rare species in Britain and infrequently recorded in the Outer Hebrides.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Ralfs, J. (1848). The British Desmidieae.
West, W. & West, G.S. (1912). A Monograph of the British Desmidiaceae, Volume 4.