Description: Thallus crustose, endosubstratic or thinly episubstratic, smooth, minutely granular or rimose-verruculose, whitish grey to ochraceous. Apothecia biatorine, brownish black, grey-brown or grey-black, rarely pale in shade-forms, rounded, sessile and constricted at base, 0.2-0.4(-0.7) mm across, with an epruinose or rarely faintly pruinose, weakly to strongly convex disc, and a thin, soon excluded proper margin. Proper exciple laterally 25-30 µm wide, of radiating hyphae, colourless or greyish green in innermost part; epithecium 5-10 µm high, patchily greenish or greyish black, N+ purple, K- or K+ intensifying green; hymenium colourless, 30-40 µm high; paraphyses coherent, simple or sparingly branched in upper part, (0.7-)1-2 µm thick at mid-level, the apical cells 4-6 µm wide, with a dark cap, the pigment deposited in the cell walls; hypothecium colourless, 60-100 µm high. Asci 8-spored, clavate, with a K/I+ blue apical dome penetrated by a narrow, K/I– apical cushion surrounded by a narrow, deeply K/I+ blue zone, the wall K/I- but surrounded by an I+ red-brown, K/I+ blue outer layer, the ocular chamber relatively small, Biatora-type. Ascospores 1-celled (rarely 1-septate), hyaline, oblong to subcylindrical, (7-)10-17 x 2-3(-4) µm. Pycnidia dark, globular, immersed, the wall dark green. Conidia conidia of two types: a) cylindrical or curved, 3.5-5 (-6) x 0.5.0.7 μm, or b) ellipsoid, 2-2.8 x 1–1.5 μm. Photobiont chlorococcoid, the cells 7-18 µm in diam. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a mainly temperate, perhaps holarctic lichen found on acid and rough bark of broad-leaved trees in sheltered situations, often in fissures, and in association with calicioid lichens. According to Printzen (2014) it firmly belongs in Biatora.