Psora decipiens (Hedw.) Hoffm.
Thallus squamulose, squamules up to 4 mm wide, more or less aggragated, apices rounded, margin slightly turned up and ascending, distinctly delimitate by a conspicuous white farinose pruine, upper surface pinkish, brown-pinkish, brownish, brown-reddish, lower surface whitish, attached to the substratum by a network of hyphae. Apothecia 1-1.5 mm diam., one per squamule, marginal, convex, more or less pruinose, black, exciple soon excluded. Ascospores ellipsoid, simple, 10-18 x 6-8 µm. Photobiont: Chlorococcoid. Chemical spot tests negative, according to some authors, or K+ yellow > reddish. Not especially maritime, on ground in calcareous dunes enriched in shell debris or on calcareous sandy soils. This species has not been found yet in Brittany.*