Protoblastenia rupestris forme sur mortier.

     This form occur on the mortar of the old walls. The thallus is thin, irregular and poorly demarcated, ochre-yellowish, earthy. Common form on mortar walls with little sunlight in chapels.

N.B. Watch out for Caloplaca crenulatella whose apothecia are less globose and have a margin (at least initially) and also a K+ thallus and polarilocular spores.