Caloplaca oasis. A very common species that used to come under the Caloplaca holocarpa. Almost all British material belongs to Caloplaca oasis. It is characteristed by the yellowish thallus, which especially in o=urban areas becomes blackened. Frequent on calcareous brick and stonework, it is here seen on a breakwater in Bexhioll on Sea.
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![](https://psl.brc.ac.uk/sites/default/files/upload/Caloplaca%20oasis.jpg)