Thallus crustose, orbicular to spreading, areolate, verrucose or continuous, white, yellowish, greenish, ashy-grey or brownish, corticate, cortex of compacted, gelatinised cells, medulla of loose hyphae, lacking a lower cortex, the lower side grading into a black, continuous or radiating prothallus. Photobiont . Apothecia lecideine, black, small, 0.2-0.5(-2) mm diam., circular or angular, disc ± plane, concave or convex in some species, ± between areolae usually on prothallus, disc smooth to minutely roughened or "sooty", black proper margin distinct in young fruits, often excluded with age. Hymenium colourless, greenish to red-brown near epithecium. Epithecium inspersed with black granules. Hypothecium dark brown, 30-55 µm tall. Paraphyses septate, strongly conglutinate, richly branched anastomosing, 1.5-2.5 µm thick, apices globose to clavate, 3-6 µm diam. Asci narrowly clavate to cylindrical 8-spored, rarely (1-)2-6-spored. Ascospores uniseriate or biseriate, 1-septate to ± muriform, colourless, pale brown to brown-black often with a greenish tinge, sometimes halonate with a gelatinous epispore 3-10 µm thick.