Distribution: N - Lig (Scheidegger 1993). S - Sar.
Description: Thallus crustose, episubstratic, rimose to rimose-areolate, chalky white to cream-coloured, sometimes subeffigurate at margins, without a distinct prothallus. Medulla faintly amyloid, I+ pale blue. Apothecia cryptolecanorine or lecideine, black, 0.4-0.7 mm across, with a flat to slightly convex, faintly white-pruinose disc, and a thin to usually poorly evident proper margin often surrounded by a thin, cracked thalline collar when young. Proper exciple aethalea-type, poorly developed, inspersed with crystals reacting C+ orange, 20-30(-50) μm wide laterally, the inner hyphae hyaline, prosoplectenchymatous, the outer hyphae parallel and usually strongly brown-pigmented; epithecium olive-brown to dark grey-olivaceous green, N+ red-violet, with abundant crystals reacting C+ orange; hymenium colourless, not inspersed with oil droplets, 60-80 μm high; apical cells of paraphyses 3-4 μm wide; hypothecium dark reddish brown, paler in upper part. Asci 8-spored, clavate to cylindrical-clavate, the apical dome K/I+ dark blue with a pale, conical-pointed apical cushion (axial mass), the wall I-, but the thin outer gel I+ blue, Bacidia-type. Ascospores 1-septate, slightly constricted at septum, brown, oblong-ellipsoid, 12-16 x 6.5-8.5 μm, at first Physconia-type, then Buellia-type, with a microfoveate ornamentation. Photobiont chlorococcoid. Spot tests: thallus K+ yellow to yellow-orange, C+ pale orange, KC+ deep orange, P-, UV+ pale orange-pink. Chemistry: arthothelin (major), atranorin (minor), thiophanic acid and 4,5-dichloronorlichexanthone (traces).
Note: a rare Mediterranean species of base-rich siliceous rocks.