Thelotrema macrosporum  

Thallus pale grey-green, often somewhat white-marbled when fresh, becoming ochraceous when dry, forming small to large superficial patches which are rather thick (up to 130 µm in thickness); medulla with coarse calcium oxalate crystals.
Anamorph: not known.
Teleomorph: ascomata apothecia, (0.7-) 0.8-1.2 (-1.5) mm diam., immersed in hemispherical warts, somewhat flattened at their summits, urceolate, the ostiolar opening usually narrow, 0.2-0.4 (-0.7) mm wide; true exciple colourless, inapparent when seen through the ostiole; thalline exciple entire; hymenium (100-) 140-200 µm tall. Asci 130-170 × 40-55 µm, 1- (to 2-) spored. Ascospores (70-) 90-120 (-160) × (15-) 25-40 (-50) µm, broadly fusiform with rounded ends, opaque grey-brown when mature, with 16-22 (-24) transverse and numerous longitudinal septa, I–, with a gelatinous coat.
Chemistry: thallus and medulla C–, K–, KC–, Pd–, UV– (lichen products not detected by TLC).