Phylum: Chlorophyta   Family: Closteriaceae

Closterium archerianum P.T. Cleve ex P.M. Lundell 1871

First described by Cleve in Lundell (1871: 77, pl. 5: 13). The striations vary from barely visible to quite pronounced.
Cell dimensions: L: 200-250 µm; B: 16.5-22 µm; Ap: 3.5-5 µm; Arc: 135-149°; L/B: 10-13.
In the Outer Hebrides, this is a rare species. Found in peaty, acidic conditions.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Brook, A.J. & Williamson, D.B. (2010). A Monograph on some British Desmids.
Lundell, P.M. (1871). De Desmidiaceis, quae in Suecia inventae sunt, observationes criticae.