Phylum: Charophyta   Family: Desmidiaceae

Staurastrum subavicula (W. West) W. & G.S. West 1894

First described and illustrated by West (1892: 732, pl. 9: 25) as Staurastrum arcuatum subsp. subavicula. Two years later West & West (1894: 12) comment: “Dr. 0. Nordstedt (in litt.) has pointed out that this cannot be a variety of his S. arcuatum, consequently it must rank as a distinct species.” (The statement wasn’t qualified.) However, this taxon is sufficiently distinct, especially in body-shape to warrant species rank.
Cell dimensions: L: 32-35 µm; B: 30-35 µm; Is: 9.5-12.5 µm.
A species of acidic habitats including with Sphagnum. It is proving to be scarce in the Outer Hebrides.

References: 
West, W. (1892) Algae of the English Lake District.
West, W. & West, G.S. (1894) New British freshwater algae.