Phylum: Charophyta   Family: Desmidiaceae

Staurastrum striolatum (C. Nägeli) W. Archer 1861

It’s closely related to S. alternans and S. dilatatum and is regarded as a problematic complex. Two features that help to distinguish this species: the apex in face view is largely truncate and the apex of the sinuses is notched. The zygospores of this complex are virtually identical.
It’s rarely recorded in mesotrophic habitats such as moorland pools and loch-margins. It can be found in slightly acidic waters.
Cell dimensions: L: 21-30 µm; B: 20-36 µm; Is: 7.0-8.0.

References: 
Archer, W. in Pritchard, A (1861). A history of infusoria, including the Desmidiaceae and Diatomaceae, British and foreign.
Coesel, P.F.M. & Meesters, K.J. (2023 second edition) Desmids of the Lowlands.
Nägeli, C. (1849) Gattungen einzelliger Algen, physiologisch und systematisch bearbeitet.
West, W. & West, G.S. (1912) A Monograph of the British Desmidiaceae, Volume 4.