Catapyrenium cinereum  

Thallus of small, ± densely aggregated squamules, to 0.3 mm thick, rarely more than 2 mm across, closely appressed, finely incised especially at the periphery, sometimes subgranular in central parts of thallus, usually whitish pruinose, rarely naked and brown, often with a darker margin; lower cortex blackish; hypothallus blackish, spongy, of intricately interwoven rhizoidal hyphae ca 4 μm diam.
Anamorph: not known.
Teleomorph: ascomata perithecia, numerous, immersed in the squamules, the ostioles sometimes slightly elevated; true exciple pale when young, soon becoming brown or blackish throughout. Asci clavate. Ascospores 17-23 × 6-9 μm, usually ± clavate, biseriate, rarely 1-septate.