Distribution: N - Ven, Lomb (Alessio & al. 1995), VA (Piervittori & Isocrono 1999).
Description: Thallus foliose, heteromerous, dorsiventral, olive-brown to dark brown, dull to slightly glossy in marginal parts, forming up to 15 cm wide rosettes. Lobes to 5 mm wide, slightly raised at margins, wrinkled, bearing obscure to distinctive, punctiform, laminal pseudocyphellae, which are best visible in the marginal parts; lower surface dark brown, paler in marginal parts, with mostly simple rhizines. Upper cortex paraplectenchymatous, with a non-pored epicortex, the cell walls containing isolichenan; medulla white; lower cortex paraplectenchymatous. Apothecia frequent, lecanorine, to 9 mm across, often crowded in central parts of thallus, with a concave to finally convex, brown disc, and an entire to finally strongly crenulate thalline margin with punctiform to somewhat elongated pseudocyphellae. Epithecium brown; hymenium colourless, 50-110 μm high; subymenium rather thick, 20-45 μm high; hypothecium colourless, 10-40 μm high. Asci 8-spored, clavate, Lecanora-type. Ascospores 1-celled, hyaline, ovoid to ellipsoid, 12-17 x 7-11 μm. Pycnidia frequent, black, laminal. Conidia more or less dumbbell-shaped, c. 8 x 1 μm. Photobiont chlorococcoid. Spot tests: upper cortex K-, C-, KC-, P-; medulla K- or rarely K+ yellow, C-, KC-, P+ orange. Chemistry: fumarprotocetraric acid, protocetraric acid (sometimes only in traces), sometimes atranorin in low amounts.
Note: a circumboreal-montane species, mostly found on Betula in cold, but sunny situations and in upland areas. The epithet "olivacea" was used in the past for several other species of this group; all earlier records from Italy are unreliable, including that of Ahti from the Euganean Hills (see Nimis 1993: 479); the recent ones from Lombardia and Valle d'Aosta need confirmation. The species, however, was recently reported from several localities in Switzerland.