Phylum: Chlorophyta   Family: Chlamydomonadaceae

Chlamydomonas britannica J.W.G.Lund 1947

First described and illustrated by Lund (1947: 193, fig. 3 J-K). [AlgaeBase now have this listed as Chlamydomonas eustigma Ettl, but without date or reference. I’ve not been able to trace it so presume it’s a mistake]. NBN still have it as C. britannica.
Cell dimensions: L: 12-16 µm; B: 8-14 µm.
Rarely recorded; mainly described from some English soil cultures.

References: 
John, D.M., Whitton, B.A. & Brook, A.J. (2011 second edition). The Freshwater Algal Flora of the British Isles.
Lund, J.W.G. (1947). Observations on soil algae III. Species of Chlamydomonas Ehr. in relation to variability within the genus.