Lecanora gangaleoides Nyl.
Common and widely distributed on siliceous rocks at coastal sites and also inland. Requires careful examination to separate it from the very similar Tephromela atra
Smith, C.W. et al. editors (2009) The Lichens of Great Britain and Irelandd
Dobson, F.S. (2018) Lichens: an Illustrated Guide to the British and Irish Species