Phylum: Chlorophyta   Family: Scenedesmaceae

Tetradesmus dimorphus (P.J.F. Turpin) M.J. Wynne 2016

First described and illustrated by Turpin (1828: 313, pl. 13: 12) as Achnanthes dimorpha. It was moved much later to its current taxonomic position by Wynne (2016: 84).
Cell dimensions: L: 6-25 µm; B: 2-10 µm.
A fairly common planktonic species, found in circum-neutral water.

References: 
John, D.M., Whitton, B.A. & Brook, A.J. (2011 second edition). The Freshwater Algal Flora of the British Isles.
Turpin, P.J.F. (1828). De la description de plusieurs genres et espèces nouvelles très remarquables, découverte parmi les productions végétales et microscopiques.
Wynne, M.J. & Hallan, J.K. (2016). Reinstatement of Tetradesmus G. M. Smith (Sphaeropleales, Chlorophyta).