According to the British Flora in the British islands, and by extension I believe the same can happen here, there are only four Caloplaca spp. satysfying the following conditions: - Grow on (calcareous or siliceous) rocks; - Thallus entirely corticate without isidia, blastidia or soralia; - Disc yellow, orange or rust coloured when dry; Thalline margin disappearing with age; - Cortex white or grey, K- (only discs usually K+ purple) - Ascospore septum >1/8 lenght of spore; Namely , C. arenaria, C. ceracea, C. crenularia, C. holocarpa agg. . To note that the last one is an aggregate of taxa, that the authors consider not to be yet completely resolved. It happens that quite recently I believe to have found three of these species, only C. arenaria being absent from those observations.