Rust-coloured, areolate, crustose thallus with black prothallus. Numerous immersed apothecia, concave, with raised margins. On exposed, hard, siliceous rocks, mainly in upland areas

Determiner: 
Chris 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