Phylum: Charophyta   Family: Desmidiaceae

Micrasterias truncata J. Ralfs 1848

The main characteristics of this nominate variety are the closed sinus and predominantly closed invaginations between the major lobes. There are several varieties, the commonest one being M. truncata var. semiradiata.
Cell dimensions: L: 103-124 µm; B: 94-115 µm; Is: 22-26 µm; L/B: 1.00-1.10.
West & West (1905: 84) note: “This is one of the most abundant species of the genus, more especially in the Sphagnum bogs and pools of upland districts.” This is no longer the case in the Outer Hebrides, it is now infrequently encountered. The habitat is acidic mesotrophic waters such as moorland pools and abandoned peat-cuttings.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Van Westen, M.C. (2024). Sieralgen in Drenthe.
West, W. & West, G.S. (1905). A Monograph of the British Desmidiaceae, Volume 2.