Myriolecis antiqua (J. R. Laundon) Sliwa, Zhao Xin & Lumbsch
Lecanora conferta auct. brit.
Lecanora antiqua J. R. Laundon
Thallus crustose, insignificant, in the form of a "veil" without hypothallus or reduced to scales or granules and often inconspicuous or evanescent and hardly visible, dull grey, dull cream, greyish. Apothecia generally very numerous, ordered in streaks or more or less crowded in small clusters, disc flat, pale brown, pale brown-greyish, exciple thick and conspicuous, as covered with snow (not crenulate stricto sensu), most often persistent and seldom excluded when old, whitish. Ascospores simple, colourless, ellipsoid, 8-12 x 4-7 µm. Photobiont: Trebouxia. Thallus: C- or C + / + weak yellow, K- or K +/- weak yellow, KC +/- weak yellow, P-; margin of apothecia: C + golden yellow, brown-orange, K + yellow, KC + brown-orange; disc: C + brown-orange. Usually on granite of old walls slightly alkaline owing to the above mortar bleaching.
N.B. Lecanora conferta ss. str. would have a darker thallus, apothecia with browner discs and exciple excluded when old, on more alkaline rocks.
Cf. Very resembling species like those of the Lecanora semipallida / dispersa group have a browner disc and negative chemical spot tests. Lecanora crenulata is more grey-blueish and has crenulate exciple as well as negative chemical spot tests. Myriolecis fugiens occurs on more acidic rocks and is also C+ orange but P+ orange.