Phylum: Chlorophyta   Family: Hydrodictyaceae

Stauridium tetras (C.G. Ehrenberg) E. Hegewald 2005

First described and illustrated by Ehrenberg (1838: 155, pl. 11:1) as Micrasterias tetras. He later moved it to the genus Pediastrum tetras, in Ralfs (1845). More recently, it was moved again by Hegewald (2005: 1051) to its current position. Variable in shape depending on the number of cells in each coenobium.
Cell diameters: 12-25 µm.
Found in the phytoplankton and benthic layer in moorland pools and shallow bogs.

References: 
Ehrenberg, C.G.(1838) Die Infusionsthierchen als vollkommene Organismen. Ein Blick in das tiefere organische Leben der Natur.
Hegewald, E. in Buchheim, M. et al. (2005) Phylogeny of the Hydrodictyaceae (Chlorophyceae): inferences from rDNA data.
John, D.M., Whitton, B.A. & Brook, A.J. (2011 second edition) The Freshwater Algal Flora of the British Isles.
Ralfs, J. (1845) On the British Desmidieae.