Phylum: Charophyta   Family: Desmidiaceae

Micrasterias americana J. Ralfs 1848

First described and illustrated by Ralfs (1848: 74, pl. 10: 1) as Micrasterias morsa without authorship. In the same work (l.c.: xix, Errata and Addenda) it was emended to M. americana. West & West (1905: 117, pl. 53: 4-5 & 54: 1-3) note: “… is principally characterized by the form of its lateral lobes. It has a wide distribution in the British Islands, but is an uncommon species.” Interestingly, the larger number of records are from Scotland but none for either the Inner or Outer Hebrides.
Cell dimensions: L: 125-150 µm; B: 100-145 µm; Is: 17-30 µm; L/B: 0.95-1.25.
A rarely recorded acidophile, found in moorland bogs 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. (1905) A Monograph of the British Desmidiaceae, Volume 2.