Phylum: Charophyta   Family: Desmidiaceae

Euastrum rhomboidale (F. Ducellier) P.F.M. Coesel & K.J. Meesters 2023

Originally described and illustrated by Ducellier (1918: 44, figs. 26-28) as Euastrum ansatum var. rhomboïdale. Coesel & Meesters (2023: 97, pl. 47: 7-8) raised it to species rank. It differs from E. ansatum by lacking lateral lobes and a smoother progression into the apices. The apical section in E. ansatum has almost parallel sides. E. rhomboidale also has a broader isthmus.
Cell dimensions: L: 70-110 µm; B: 40-53 µm; Is: 16-17 µm; L/B: c.2.0.
A rare species of acidic habitats.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition) Desmids of the Lowlands.
Ducellier, F. (1918) Étude critique sur Euastrum ansatum Ralfs et quelques-unes de ses variétiés Helvétiques.