Halecania ralfsii (Salwey) M. Mayrhofer

    Thallus crustose, more or less effuse, 2-6 cm across, rimose, cracked, made of convex areoles organized as a 'macaronis dish', or like if tooth paste had been spread, surface striated or pleated or even graven, waxy textured, typically grey-blue to leaden-grey or slate-grey, bluish spotted with brown or green in eroded places. Apothecia usually rare, 0.2-0.5 mm diam., urn-shaped and prominent at first, then slightly laid on thallus, disc mostly flat at first then slightly convex, dark brown to black, paler when old, thalline margin concolorous with thallus, possibly vanishing with age. Pycnidia numerous visible as minute black dots. Ascospores broadly ellipsoid, 1-septate with one perispore (clearly visible and swollen in K), 15-17 x 6-9 µm. Photobiont: chlorococcoid. Cortex: C-, K +/- yellow, KC +/- yellow, P +/- red-orange; medulla: C-. K-, KC-, P + red-orange. Rare and localized species (but often abundant in its stations) occurring on the very exposed siliceous rocks of the mesic zone, sometimes associated with Lecanora helicopis which can be confused because this last species is sometimes also gray-bluish, but it is P- and comes in sunnier areas, also with Lecanora actophila also P-.

N.B. This species is frequently associated with the maritime Verrucaria of the black belt and in particular with Hydropunctaria (Verrucaria) maura grp. and Verrucaria erichsenii of which it is possibly a parasite.

N.B. Halecania laevis has recently been separated from this species, which is very similar and sometimes occurs in the same habitat and often mixed together, but which has a smoother thallus with dirty whitish spots in eroded areas and less "spread toothpaste", slightly smaller spores and is mostly P- on the medulla.