Lecidea phaeops Nyl.
Thallus variable in colour from white to greenish, also variable in the amount of crazing. On siliceous rocks with good moisture such as overhangs
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