Trapelia glebulosa (Sm.) J. R. Laudon

    Thallus crustose-squamulose, made of squamulose areoles more or less separate, usually dispersed but sometimes mostly contiguous or overlapping, crust forming, squamulose at the edge, squames 0.2-0.4 mm diam., convex to markedly convex when separate, bright to white-bluish, whitish, white-glaucous. Apothecia 0.4-0.8 mm diam., almost embedded within sqamules at first (eye-like), then sessile, disc flat  to convex or markedly convex (and even globose when moist), sometimes uneven, brown-red, dark red to very dark red, exciple very thin to absent when mature, minutely squamulose, paler or whitish. Ascii 8-spored, clavate to cylindrical, K/I-, 90-130 x 20-25 µm (according to our own measures). Ascospores colourless, simple, ellipsoid, external wall tender, easily torn within a K solution (potentially suggesting polarilocular ascospores), 15-26 x 7-13 µm. Photobionte: chlorococcoid. C+ red, K-, KC+ red, Pd-. On siliceous rocks (granite or schists) or more frequently on stony grounds where apothecia are more developed. See Trapelia coarctata of which the thallus is granular without squames.