Porpidia macrocarpa (DC.) Hertel & A.J. SchwabThallus crustose, endolithic or thinly epilithic, continuous to rimose-areolate, white, yellowish white, or pale grey, rarely ochre-coloured, sometimes delimited by a dark prothallus. Medulla white, I-. Apothecia lecideine, more or less round, sometimes clustered, slightly constricted at base, 1-4 mm across, with a black, flat to convex, sometimes slightly pruinose disc, and a more or less persistent, usually entire, thick and tumid (0.15-0.25 mm thick), raised proper margin. Proper exciple black to dark brown in outer part, paler and K- within (rarely K+ yellow), with 3-9 µm wide hyphae; epithecium brown or olivaceous brown; hymenium colourless, I+ blue, 90-130(-150) µm high; paraphyses sparingly branched and anastomosing; hypothecium pale to usually dark brown. Asci 8-spored, elongate-clavate, with a thin, outer amyloid layer and a thickened tholus penetrated by a pore, the sides of which are strongly amyloid, <i>Porpidia</i>-type. Ascospores 1-celled, hyaline, ellipsoid, (16-)18-25(-28) x (5-)7-11(-14) µm. Photobiont chlorococcoid. Spot tests: thallus K- or K+ yellow, C-, KC-, P- or P+ orange. Chemistry: stictic acid (major), constictic, norstictic and cryptostictic acids (all minor or trace), or without lichen substances. 