Phylum: Charophyta   Family: Desmidiaceae

Staurastrum dilatatum J. Ralfs 1848

Ralfs’ (1848: 133, Pl. 21: 8) original description was poorly figured so the concept of the species presented by West & West (1912: 173, pl 126: 11) has been adopted. It’s closely related to S. alternans and S. striolatum, although slightly larger with a broader isthmus, and is regarded as a problematic complex. The zygospores of this complex are virtually identical.
It’s frequently recorded in mesotrophic habitats such as moorland pools and loch-margins. It can be found in slightly acidic waters.
Cell dimensions: L: 28-37 µm; B: 29-42 µm; Is: 11.0-16.0.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition) Desmids of the Lowlands.
Ralfs, J. (1848) The British Desmidieae.
West, W. & West, G.S. (1912) A Monograph of the British Desmidiaceae, Volume 4.