Phylum: Charophyta   Family: Desmidiaceae

Staurastrum aculeatum J. Ralfs 1848

Cells slightly broader than long, deeply constricted and predominantly 3-radiate. The sinus is V-shaped at its apex and opens widely. Semicells sub-fusiform to sub-elliptical, with the lateral angles slightly or not at all produced, terminating in three or four strong spines. The rest of the semicells are extravagantly ornamented with mainly simple spines with some bicuspid denticulations near the centre of the apices and submarginally.
Cell dimensions: L: 45-61 µm; B: 48-70 µm; Is: 16-18.5 µm; L/B: 0.87-0.98.
Found in acidic habitats such as moorland pools and bogs. It has a wide geographical distribution but never common.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
West, W., West, G.S. & Carter, N. (1923). A Monograph of the British Desmidiaceae, Volume 5.