Thallus pale olivaceous or grey-green or grey-white, thin, continuous, irregulary cracked to areolate-cracked, matt or shining, 2-4 cm diam.,in irregular patches, with a thin, black, wavy marginal prothallus, corticolous. Fertile verrucae not much raised above thallus, sparse, blisterlike, ± convex, 1-2 mm diam., concolorous with thallus, apices flattened. Apothecia immersed, 1-5 per verruca, ostioles minute, brown or black, punctiform. Asci clavate, 8-spored. Ascospores uniseriate, oval-ellipsoid 51-69 × 18.7-26(-30) µm, wall 1.5-2.5 µm thick. Chemistry: K+ yellow, Pd+ orange. Thamnolic acid.