Family: Fuscideaceae
Fuscidea cyathoides (Ach.) V. Wirth & Vězda
Type: Crustose
Mosaic-forming with a dark, usually black, prothallus. Variable in colour, greyish-brown is the most common, on siliceous rocks and stabilized shingle
References:
Smith, C.W. et al. editors (2009) The Lichens of Great Britain and Irelandd
Whelan (2011) Lichens of Ireland