Phylum: Charophyta   Family: Peniaceae

Penium spirostriolatum  J. Barker 1869

First described by (Barker 1869: 194). Cells subcylindrical with a slight median constriction gradually attenuating to truncately-rounded apices. Cell-wall covered with longitudinal rows of striae or series of small granules.
Cell dimensions: L: 100-250 µm; B: 15-30 µm; L/B: 5-15.
Infrequently recorded, found in oligotrophic, acidic bogs, especially with Sphagnum.

References: 
Barker, J. (1869) A new and remarkable species of Penium (P. spirostriolatum).
Coesel, P.F.M. & Meesters, K.J. (2023 second edition) Desmids of the Lowlands.
Ruzicka, J. (1977) Die Desmidiaceen Mitteleuropas, Volume 1, Part 1.
West, W. & West, G.S. (1904) A Monograph of the British Desmidiaceae, Volume 1.