Phylum: Charophyta   Family: Closteriaceae

Closterium costatum J. Ralfs 1848

First described in Ralfs (1848: 170, pl. 29: 1) and illustrated by Jenner.
Cell dimensions: L: 270-400 µm; B: 33-52 µm; Ap: 12.5-14 µm; L/B: 7-8.
A common acidophile, especially associated with Sphagnum bogs, peaty pools and abandoned peat-cuttings.

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.