Distribution: C - Tosc (Ravera & al. 2022), Sar (B-Leg. H. Sipman nr. 24073).
Description: Thallus crustose, episubstratic, rather thick, verrucose-areolate, pale glaucous grey to ochraceous grey, rarely delimited by a thin, dark prothalline line. Medulla white, I-. Apothecia black, lecideine, 0.3-0.8(-1) mm across, initially immersed, then slightly prominent, with a black, flat to convex, epruinose or faintly pruinose disc, and a thin, finally excluded proper margin. Proper exciple brown in outer part, colourless to pale brown in inner part, of radiating hyphae; epithecium brown; hymenium colourless, K/I+ blue; paraphyses simple, c. 2 μm thick at mid-level, the apical cells up to 3 μm wide; hypothecium brown. 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, approaching the Bacidia-type. Ascospores at first 3-septate, then submuriform, brown, ellipsoid, 12-22 x 7-11 µm. Photobiont chlorococcoid. Spot tests: K-, C- KC-, P-, UV-. Chemistry: without lichen substances.
Note: a saxicolous taxon of the D. alboatrum-group with a grey-white, verrucose to areolate thallus, found on various types of rocks near the seashore, widely distributed along the Atlantic and Mediterranean coasts of Europe. According to Roux & coll. (2014) this is a good species, differing from D. alboatrum in morphological characters and in the ecology; the Italian sample, identified by H. Sipman, was collected at Capo Falcone (Sassari), on siliceous schist boulders and outcrops, on steep slopes with garrigue at seashore, just above highwater level.