Species: Sticta fuliginosa agg.
Photos: On ash. Gougane Barra, Ireland.
Now split into four separate species: Sticta fuliginosa s. str, Sticta atlantica, Sticta fuliginoides and Sticta ciliata
Most frequent in the west of Ireland on damp mossy trees and rocks in old oceanic woodland.
Chemical reactions negative. Thallus smells of fish when wet.
Details and descriptions from Neil Sanderson: Link
Photo above: Sticta fuliginosa. Gougane Barra, Co. Cork. February 2009