Apothecia: black, semi-immersed to sessile, +round, 0.25 exciple: dark brown, 30-60 µm thick, in the marginal part cells arranged in indistinct radial rows, composed of ellipsoid to +round cells 4-7 µm in diam. hymenium: hyaline, 65-85 µm tall paraphyses: septate, in the upper half, sometimes with ramifications, 2-3 µm wide, with tips enlarged up to 6 µm provided with pigment caps hypothecium: pale brown, 50-80 µm thick asci: subclavate to broadly cylindrical, 40-55 x 11-16 µm, 8-spored ascospores: dark brown, 1-septate, with spore cells of more or less equal size and shape, 9-15 x 4.5-7.5 µm; wall: relatively thick, smooth Conidiomata: not observed. Hosts: Pertusaria arizonica (= P. tejocotensis); hosts known outside the Sonoran region: Pertusaria flavicans, World distribution: widely distributed in Europe, also known from Asia, northern Africa, North America (U.S.A., Greenland) and Australia Sonoran distribution: so far known only from a relatively small area in southern Arizona. Notes: Apothecia of Dactylospora saxatilis on sterile host lichens (e.g. Pertusaria flavicans) often do have the external appearance of genuine ascomata of the host, for which they were mistaken from time to time even by experienced lichenologists. Therefore, in older literature the species is often considered a Buellia species. However, this problem does not exist in the Sonoran region in so far as there the fungus is only known on a fertile Pertusaria.