Caloplaca stillicidiorum  

Similar to Caloplaca cerina s. lat., but with a scurfy, green-grey thallus, apothecia with thick, grey, somewhat flexuose thalline margins and a plane, often green, pruinose disk, and different habitat preference. K reactions as for C. cerina. The ascospores appear to be slightly longer than those of C. cerina, but it is not clear whether this is a reliable diagnostic character for GB populations.