Xanthoria calcicola, similar to Xanthoria parietina but differs in being generally less fertile, and being covered in knob like isidia. It is a common species, but usually occurs most often on artificial man-made habitats such as concrete. Like X. parietina, it will occur on habitats enriched by bird droppings. This photograph taken in Ripe Churchyard in east Sussex.
Comments
How common would you say this
How common would you say this one was? I'm guessing it's way less common that parietina.