Phylum: Charophyta   Family: Desmidiaceae

Staurastrum hirsutum  C.G. Ehrenberg ex J. Ralfs 1848

First described and illustrated by Ehrenberg in Ralfs (1848: 127, pl. 22: 3). Cells slightly broader than long to almost as broad as long. This taxon can be confused with the similar St. brebissonii, best separated by the apical view: almost straight-sided in hirsutum; concave in brebissonii. A variable species, especially in the length of the spines.
Cell dimensions: L: 36.7-48.3 µm; B: 30.9-44.0 µm; Is: 10.7-18.5 µm; L/B: 1.04-1.22.
This species occupies habitats with quite a large pH range; from quite acidic to slightly alkaline, such as moorland lochs and ephemeral pools.

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. & Carter, N. (1923) A Monograph of the British Desmidiaceae, Volume 5.