Phylum: Charophyta   Family: Closteriaceae

Closterium parvulum var. angustum  W. & G.S. West 1900

First described and illustrated by West & West (1900: 290, pl. 412: 8). Less common than the nominate variety from which it differs by more slender cells.
Cell dimensions: L: 113-126 µm; B: 8-9 µm; Ap: 2.4-2.8 Arc: 75-96º; µm; L/B: 13-14.
Infrequently recorded from mildly acidic to slightly alkaline habitats such as moorland bogs and pools.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Van Westen, M. (2024). Sieralgen in Drenthe.
West, W. & West, G.S. (1900). Notes on freshwater algae. II.
West, W. & West, G.S. (1904). A Monograph of the British Desmidiaceae, Volume 1.