Phylum: Charophyta   Family: Desmidiaceae

Micrasterias papillifera var. pseudomurrayi L.J. Laporte 1931

Differs from the nominate variety in having all the incisions open. There are many intermediate forms which are difficult to determine so how much value can be afforded to var. pseudomurrayi is debatable.
Cell dimensions (2): L: 133-154 µm; B: 126-141 µm; Is: 17-19 µm; L/B: 1.06-1.10.
Found in acidic mesotrophic waters such as moorland pools and abandoned peat-cuttings. It would seem to be much scarcer than the nominate variety but see comment above.

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.