Phylum: Charophyta   Family: Closteriaceae

Closterium dianae var. pseudodianae (J. Roy) W. Krieger 1935

The degree of arc can be shallow or quite considerable (this will also alter with maturing cells) with some cells showing tumidity on the ventral side. It differs from the nominate variety in being slenderer.
Cell dimensions: L: 190-249 µm; B: 11-15 µm; Ap: 2.6-3.5 µm; Arc: 70-115; L/B: 16-18.
An uncommon taxon found in acidic bogs and moorland pools.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Van Westen, M. (2024). Sieralgen in Drenthe.