Phylum: Charophyta   Family: Desmidiaceae

Staurastrum paradoxum J. Ralfs 1848

Similar to St. gracile, but stockier and with more robust terminal spines. Found with tri-radiate and quadri-radiate forms, the latter being commonest and is stockier, presenting a different L/B ratio. The zygospores are multifaceted, presenting 4–6 angles in face view. The projections have furcate apices.
Cell dimensions: L: 31-42 µm; B: 38-59 µm; Is: 7.5-12 µm.
Zygospore: minus projections: 22-25 µm; overall: 34-38 µm.
Common in the plankton of acidic lochs and moorland pools.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
John, D.M. & Williamson, D.B. (2009). A Practical Guide to the Desmids of the West of Ireland.