Thallus dimorphic. Primary thallus persistent or disappearing, crustose or squamulose to foliose, hyphae rather loose, rarely dense or conglutinate. Upper cortex dense, of ± vertical hyphae. Medulla white, of thick-walled, often conglutinate hyphae. Lower surface usually decorticate. Photobiont green, , conglomerate in an irregular layer in the upper part of the medulla. Podetia, (vertical developments of the stalks of apothecia) grow from upper surface of margins of primary thallus, blunt, pointed or cup-forming (scyphiferous), simple or branched, solid at first, soon becoming hollow, with an outer cortex which may persist or disintegrate, becoming sorediate, verrucose or areolate. Soredia farinose (10-40 µm diam.), granular (40-120-300 µm diam.) often densely encrusted with lichen compounds; corticate granules (100-300 µm diam.) similar to soredia but with a well-developed ± continuous, thin corticate layer. Medulla dense or loose, containing symbiotic algae in outer part: in many species outer medulla becomes arachnoid and the inner medulla becomes hard and horny (chondroid) entirely, or in strands. Base persistent or dying away with growth continuing at apices, apices sterile or with apothecia. Apothecia at tips of podetia (normally larger than diameter of supporting stalk), on margins of cups (scyphi) or on primary squamules, lecideine, red, pale or dark brown or brown-black, margins narrow, or immarginate and convex, solitary or clustered-peltate to compound, confluent, exciple radiate, hypothecium pale to reddish, hymenium 30-70 µm tall, paraphyses slender, 2-5 µm thick, simple or sparingly branched. Asci cylindrical to clavate, 8-spored. Ascospores irregularly biseriate, fusiform, oblong or ovoid, 6-24 × 2-4.5 µm, simple, colourless. Pycnidia at apices of podetia, margins of cups, margins or upper surface of primary squamules, sessile or short-stalked, variable in shape, cylindrical, ovoid, turbinate or capitate, ostiole small or dilated, brown-black, ashy or red, containing a colourless or red jelly. Conidia cylindrical, filiform, straight or curved, 5-14 × 0.5-1 µm.