Caloplaca ulcerosa  

Thallus crustose, widespreading, grey-white, forming a thin continuous non-areolate film. Soralia to 300 µm diam., rather scattered, discrete, rarely coalescing, concave, rounded, grey- to pale yellow-green, arising from low, bursting pustules forming ulcer-like craters in the thallus. Soredia coarsely farinose.
Anamorph: no information available.
Teleomorph: ascomata apothecia, to 600 µm diam., usually present, usually scattered, emergent to sessile. Thalline margin thin, grey-white. Proper margin orange, both exciples may become excluded. Disc concave at first, soon becoming flat and then convex, bright orange. Interascal tissue of paraphyses with swollen tips, to 6 μm diam. Ascospores 8-12 × 4-8 μm, broadly ellipsoidal, the septum 3-6 μm wide, between 1/3-1/2 of the length of the ascospore.
Chemistry: thallus and soredia K–, apothecia K+ purple.