Phylum: Charophyta   Family: Desmidiaceae

Staurodesmus controversus (West & G.S. West) Teiling 1967

First described by West & West (1894: 9) as Arthrodesmus controversus. Teiling (1967: 504) later moved it to the new genus Staurodesmus. This is similar to St. crassus but that taxon is larger, without overlap in size.
Cell dimensions: L: 10-14 µm; B: 11-14 µm.; Is: 6.5-7.6 µm; Sp: 1.0-2.5.
A rare species, most likely to be found in Atlantic regions in oligotrophic acidic waters.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Teiling, E. (1967). The desmid genus Staurodesmus. A taxonomic study.
West, W. & West, G.S. (1894). New British freshwater algae.