Myriolecis actophila (Wedd.) M. Bertrand & Cl. Roux
Lecanora actophila Wedd.
Thallus crustose, crazed to cracked, usually smooth or very slightly rugose-verrucose, highly variable according to exposition and sites: cream, grey-yellowish, dull yellow, dull whitish, dull yellow-ochraceous sometimes tinged grey-bluish, prothallus whitish or blue-green. Apothecia scattered all over the thallus, usually in small numbers (to the contrary of close species growing on the same substratum), 0.5-1 mm diam., sessile to protruding, disc flat, not convex, sometimes powdery with a bluish pruine, colour depending on hydration, dark green-bluish tinged blue, grey-greenish when moist becoming blackish to dark blue when old, exciple determinate, much paler or concolourous to the thallus, slightly raised, not crenulate when old. Ascospores simple, ellipsoid, sometimes guttulate, 8-14 x 5-6 µm. Pycnidia present, dark-blue. Photobiont: Trebouxia. C-, K-, Pd-, KC+ yellowish. Highly variable species, not common but abundant in some specific areas, on top of well-lit siliceous rocks and vertical walls, sometimes on top of stone walls of harbour facilities, always within or immediatly above the Caloplaca marina and Verrucaria (Hydropunctaria) maura agg. zone. N.B. Not to be confused with Lecanora gangaleoides and Tephromela atra that are K+ yellow and with a less smooth thallus, devoid of pycnidia, and with apothecia discs black. See also Lecanora helicopis that grows in more shaded areas and of which the thallus is lead-grey and apothecia discs darker and convex at maturity.*