Variable, shiny greyish-cream crustose thallus. Numerous apothecia in barnacle-like raised warts with large central opening. On smooth and sometimes rougher bark of deciduous trees

Determiner: 
Christine Johnson

References: 
Smith et al. editors (2009) The Lichens of Great Britain and Ireland
Dobson (2018) Lichens: an Illustrated Guide to the British and Irish Species