Phylum: Chlorophyta   Family: Oocystaceae

Oocystis elliptica W. West 1892

First described and illustrated by West (1892: 736, pl. 10: 56).
Cell dimensions: L: 15-20 µm; B: 8-16.5 µm; L/B: 2.0-2.25. Coenobia usually 4, 8 or 16 celled.
Thought to be widespread in Britain, usually in the plankton. Can also be found in flowing water.

References: 
John, D.M., Whitton, B.A. & Brook, A.J. (2011 second edition). The Freshwater Algal Flora of the British Isles.
West, W. (1892). Algae of the English Lake District.