Phylum: Chlorophyta   Family: Scenedesmaceae

Coelastrum pulchrum W. Schmidle 1892

First described and illustrated by Schmidle (1892: 206, pl. 11: 1-2). There are a number of species in this genus, not always easy to identify. This is one of the commonest.
Coenobia broadly spherical, usually 8-16 celled; diameters: c.60 µm; Cell diameters: 15-23 µm.
Probably fairly common in circum-neutral waters such as loch-margins and moorland pools.

References: 
John, D.M., Whitton, B.A. & Brook, A.J. (2011 second edition). The Freshwater Algal Flora of the British Isles.
Schmidle, W. (1892) Ueber einige neue und selten beobachtete Formen einzelliger Algen.