Sarcogyne regularis Körb. var. regularis

    Thallus very thin, evanescent and inconspicous, pale greyish, dull whitish. Apothecia inserted in crevices of substratum or slightly immersed in a small shallow cup, 1-1.5 mm diam., disc brown-red to blackish when dry, dark brown-red when moist, sometimes powdery but still weakly and bluish, exciple soon excluded. Ascii club-shaped, ± 100-spored, 60-85 x 14-18 µm according to literature, 45-60 x 15-25 µm according to our measures. Ascospores ellipsoid, simple, 3-5 x 1,5-2 µm according to literature, 3-4 x 1,5-2 µm according to our measures. Hamathecium of paraphyses, simple to sparsely branched, regularly septate. Photobiont: Myrmercia. Chemical spot tests negative. Fairly common species on limestone rocks, more rarely on coarse lime mortar of old walls, sometimes concrete.

See Cf. Sarcogyne clavus maritime that grows on coastal siliceous rocks with apothecia, 1-4 mm diam., disc not pruinose and exciple crenulate. See also Sarcogyne privigna  of which the apothecia have a persistent exciple more or less irregular but not crenulate and that grows on granite.

N.B. On mortar, not to be confused with Clauzadea monticola of which the apothecia are more globose and contain 8-spored asci.

N.B. This species is very variable and many varieties have been described, in particular Sarcogyne regularis var. intermedia whose disk of apothecia appears blue with a strong pruine, which has no visible thallus and which typically occurs on the mortar of old walls.