Phylum: Charophyta   Family: Desmidiaceae

Staurodesmus phimus (W.B.Turner) K. Thomasson 1959

A small cell with wide-open sinuses that have an angular apex. Semicells are subtriangular with a concave apex. The radii are bloated and support medium-sized spines that point diagonally upwards. Cells are biradiate.
Single cell dimensions: L: 23.3 µm; B: 23.7 µm; Is: 6.8 µm; Sp: 4-5 µm; Overall LxB: 31 x 29.
A rare taxon found in acidic conditions such as moorland pools and bogs. West & West (1912: 104) note: “The typical form of this species is not known to occur in the British Islands.”

References: 
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Van Westen, M. (2024). Sieralgen in Drenthe.
West, W. & West, G.S. (1912). A Monograph of the British Desmidiaceae, Volume 4.