A crustose species with a greenish brown to orange-grey thallus that is cracked. The apothecia are orange, but may acquire a greenish tinge when wet, and become convex and contorted with age.
Though less common in some parts of the northeast and north of Scotland, Protoblastenia ruspestris is widespread on calcareous substrata including limestones, concrete and mortar. BLS distribution map
scottishlichens.co.uk 