Trapelia obtegens  

Prothallus absent or inconspicuous. Thallus of areoles to 720 μm diam. but often much smaller; with abrupt margins, often scattered, strongly convex, sometimes more flattened later, with a ± round outline or becoming slightly lobed, green-grey or normally pale brownish grey to dull grey-brown, pruinose. Soralia either absent, or sparse, or abundant; when soralia are abundant, the areoles are converted into soralia early on, and corticate areoles are inconspicuous. Cortex ca 10μm thick, with brown pigment, with a thin epinecral layer (ca 4μm) of degraded cells.
Anamorph: not known.
Teleomorph: ascomata apothecia, frequent even in sorediate morphs, to 700 μm diam., the young thalline margin often with pale stretched thalline remains. Disc pinkish brown to brown-black, rough. Ascospores 17–23 × 8·5–12·5 μm, ellipsoidal, hyaline, aseptate, thin- and smooth-walled.
Chemistry: gyrophoric acid (major), 5-O-methylhiascic acid (trace).