Phylum: Charophyta   Family: Mesotaeniaceae

Spirotaenia condensata  J. Ralfs 1848

First described and illustrated in Ralfs (1848: 179, pl. 34: 1). West & West (1904: 39) note: “This is the largest and most frequent of the British species of Spirotaenia. It occurs frequently in bogs, especially in mountainous district, …”
Cell dimensions: L: 135-280 µm; B: 15-30 µm; L/B: 5-9.
This is still frequently found in moorland pools, abandoned peat-cutting and similar acidic habitats, as in the Wests' time.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition) Desmids of the Lowlands.
Ralfs, J. (1848) The British Desmidieae.
West, W. & West, G.S. (1904) A Monograph of the British Desmidiaceae, Volume 1.