Thallus crustose, rust-coloured, rarely grey-black or ochre-coloured in exposed situations, notably areolate, I-. Prothallus conspicuous, dark grey-black. Photobiont trebouxioid. Anamorph: conidiomata pycnidia, immersed in the areoles. Conidia 3-6 × 1-1.5 μm, bacilliform. Teleomorph: ascomata apothecia, 0.1-0.5 (-0.7) mm diam., numerous, neatly rounded between areoles, concave, with raised proper margins, composed of radially arranged, thick or dark brown hyphae, ± black and friable, becoming angular when contiguous, shining. Hymenium 65-80 μm tall, colourless or green. Proper margin and hypothecium K+ diffusing purple. Asci clavate, with a thin I+ blue outer gelatinous coat, the tholus well-developed, K/I± weakly blue, without a distinct ocular chamber or internal apical beak, 8-spored. Ascospores 10-15 (-17) × 6-9 (-10) μm, ellipsoidal, aseptate, colourless, smooth. Chemistry: thallus and medulla C–, K–, KC–, Pd–, UV– (unidentified rust-coloured pigment in the cortex).