Phylum: Basidiomycota Family: Incertae Sedis
Tetracladium setigerum (Grove) Ingold
An Ingoldian (freshwater-borne) hyphomycete, with three finger-like elements.
References:
Descals, et al - Preliminary Key to the British Ingoldian Aquatic Hyphomycetes, 1989
Gulis, et al - An Illustrated Key to the Common Temperate Species of Aquatic Hyphomycetes, 2005