Thallus crustose, rather thick, pale to dark grey, greenish or brownish, composed of scattered, incised, subsquamulose warts 0.1-0.4 mm diam., that soon coalesce, become sorediate and at length form a thick, contiguous, leprose sorediate crust. Photobiont a chlorococcoid alga, with cells 5-12 μm diam. Anamorph: conidiomata pycnidia with filiform conidia 13-14 x ca 1 µm in size. Teleomorph: ascomata apothecia, 150-350 (-600) µm diam., lecideine, sessile, typically forming dense, ± substipitate botryose clusters. Disc dark brown to brown-black, sometimes greyish pruinose, flat or weakly convex, sometimes slightly concave. Margin thin, persistent, typically pale to dark brown and paler than the disc, ± pruinose when young, composed of densely entangled hyphae with ± rounded cell lumina, often inspersed with granules. In section patchily dark brown with a greenish or reddish hue and with a dark brown outer edge. Hymenium colourless to pale brownish, 35-55 μm thick, with a brown to red-brown granular epithecial layer that dissolves and becomes colourless in KOH. Hypothecium dark brown, inverted cone-shaped. Interascal tissue of paraphyses 0.7-1.5 μm diam., weakly to moderately branched and anastomosing, with a brown apical cell 1-2 μm diam. Asci 28-33 × 6-10 μm, Micarea-type, lacking a well-developed ocular chamber, with a K/I+ blue tholus pierced by an inconspicuous, darker blue tubular structure, 8-spored. Ascospores 7-11.3(-16) × 3-3.9(-5) μm, ellipsoidal, hyaline, aseptate or rarely 1-septate, without a gelatinous sheath or epispore. Chemistry: thallus K–, KC–, C–, Pd–, UV+ white (perlatolic acid).