Phylum: Charophyta   Family: Desmidiaceae

Micrasterias thomasiana var. notata (O. Nordstedt) R. Grönblad 1920

It differs from the nominate variety by having the isthmial cell sculpture comprise three uniform protuberances rather than the more elaborate supported by the nominate variety. It should be carefully compared with Micrasterias denticulata, which is similar in size and ecology. One small difference is the apical lobe, smooth in M. denticulata, sporting a small spicule in M. thomasiana var. notata.
Cell dimensions: L: 220-280 µm; B: 180-250 µm; Is: 27-52 µm; L/B: 1.10-1.20.
Found in acidic mesotrophic waters such as moorland pools and abandoned peat-cuttings, but infrequently recorded. However, it is more common that the nominate variety.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
West, W. & West, G.S. (1905). A Monograph of the British Desmidiaceae, Volume 2.