Description: Thallus crustose, episubstratic, continuous to rimose, white, creamy white or pale brownish grey, smooth to farinose, ecorticate, with a thick epinecral layer filled with crystals, sometimes delimited by a thin dark prothallus. Apothecia lecideine, black, adnate to sessile, round to slightly irregular in outline, 0.4-1.2 mm across, with a slightly concave to slightly convex, epruinose disc, and a thin, smooth, rarely finally excluded proper margin. Proper exciple orange brown to dark brown, usually not extending below the hymenium (rarely closed), 60-160(-250) µm thick at base; epithecium dark reddish brown, granulose; hymenium colourless to pale brown,110-200 µm high, I+ pale red, K/I+ pale blue; paraphysoids richly branched in upper part, not coherent, c. 1.5 µm thick at base, the apical cells up to 4 µm wide; subhymenium colourless to pale yellowish brown in lower part, 90-180(-220) µm high, I+ reddish or deep blue, K/I+ deep blue. Asci (6-)8-spored, clavate to subcylindrical, the wall slightly thickened at top at maturity, I+ yellowish brown, the apical dome K/I+ blue, with a K/I- central area. Ascospores 9-17(-25)-septate, acicular or cylindrical, straight or slightly curved, (42-)60-95(-120) x 2-4(-5) µm. Pycnidia semi-immersed, the wall brown in upper part, colourless at base. Conidia cylindrical, slightly curved, 8-14 x c. 1 µm. Photobiont trentepohlioid. Spot tests: thallus K-, KC-, C-, P-, UV-. Chemistry: without lichen substances.
Note: a mild-temperate to humid subtropical, Mediterranean-Atlantic lichen found on acid bark of mature, isolated, mostly broad-leaved trees, especially Quercus and Olea, occasionally on siliceous rocks, often near the coast in Tyrrhenian Italy. Some records could refer to var. convexa.
Growth form: Crustose
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)