Caloplaca chalybaea. The second of the Caloplaca species lacking in yellow or orange pigments. This species is less common than variabilis. It usually has a paler, thicker thallus, often with a radiating margin, and the fruits are more crowded, and often darker. It is found on hard limestone, and on buildings and has been found on bridge parapets. This photograph was taken at West Asby in Westmorland. As with all Caloplaca species, the spores are polarilocular, that is they contain two separated chambers connected by a thin septum.  To be confirmed, the spores should be checked as there are species, such as some belonging to Aspicilia mwhich can look very similar.