Psilolechia lucida (Ach.) M. Choisy

    Thallus crustose, thickness variable, rough and potentially areolate, minutely leprose to granulose owing to granular soralia, sulphur yellow, somewhat yellow when shaded. Apothecia usually in limited number, inconspicuous since immersed in the thallus, 0.2-0.3 mm diam., disc convex, pale orange, occasionally apothecia are tuberculate, notably towards the edges and in that case, much larger and distinct: 0.3-0.7 mm. Ascospores colourless, oblong, simple, Photobiont: Trebouxia occasionally with Stichococcus. Chemical spot tests negative, UV+ orange, K/UV+ jaune. Not especially maritime, but not rare within crevices under overhangs of siliceous rocks or walls, usually protected from direct rain and light.

N.B. In case small thalli are found in crevices, it also is recommended to search apothecia on thin stipes of  Chaenotheca furfuracea. 

N.B. See also Chrysothrix chlorina  of which the infertile thalli may cover large surfaces, and usually grow in much more lit areas.

N.B. Psilolechia lucida with Stichococcus photobiont may be host to Microcalicium arenarium.