Phylum: Cyanobacteria   Family: Scytonemataceae

Heteroscytonema crispum (Bornet ex De Toni) G.B.McGregor & Sendall

A recent name-change - better known as Scytonema crispum. Fairly common in flowing freshwater and wet rocks

References: 
John, D.M., Whitton, B.A. & Brook, A.J. (2011 second edition) The Freshwater Algal Flora of the British Isles