Thallus crustose, epiphloeodal or rarely hypophloeodal, cortex dense, often splitting and exfoliating or, less commonly, loosely organised, lacking in hypophloeodal species. Medulla well-developed to nearly hypophloeodal. Photobiont green, , arranged as in . Apothecia emergent or rarely immersed, with a distinct thalline rim, incurved to suberect, usually forming a discrete pore. Exciple fused, carbonised, central columella often present, carbonised, simple to reticulate. Ascospores colourless or brown, transversely septate or muriform, I+ blue or rarely I—.