Opegrapha rupestris  

Thallus not apparent, the ascomata developing singly or in small clusters on the thallus surface of  its host lichens.
Anamorph: conidiomata pycnidia. Conidia 3.5-5 × ca 0.8 µm.
Teleomorph: ascomata apothecia, lirellate, 300-450 x 180-300 µm, 150-200 µm tall, black, unbranched, rectangular to almost elliptical in outline, straight or slightly curved, not spreading at the base, the ends obtuse to almost truncate, sometimes eventually becoming confluent. Disc slit-like, ± exposed at maturity; margin slightly turgid, rounded, the surface finely rugose, matt, epruinose. Epithecium poorly developed, the upper part of the paraphyses immersed in a pale brown gelatinous layer. Hypothecium poorly defined, the asci and paraphyses developing from a narrow pale brown basal layer of tissue. Interascal tissue composed of thick-walled paraphyses 2-2.5 µm diam., irregular and sparingly branched in the upper part. Asci cylindric-clavate, shortly stalked or almost sessile, very thick-walled, fissitunicate, the apex rounded and strongly thickened with a distinct apical cushion, 8-spored. Ascospores arranged biseriately, 14-22 x 5-8 µm, cylindrical to cylindric-ellipsoidal, sometimes very slightly clavate, the ends rounded, 3-septate, slightly constricted at the septa, hyaline but with an epispore that becomes brown when over-mature, smooth, gelatinous sheath and appendages absent.
Chemistry: exciple in section dull fuscous-olive brown in water, dull olive brown in K, red-purplish brown in N.