Lepra monogona (Nyl.) Hafellner =Pertusaria monogona Nyl.

    Thallus crustose, rather variable, thick, greyish, tan, cracked, areolate, with more or less elevated tubercles on top of which warts emerge, hosting apothecia, 1-6 apothecia per wart. Apothecia deeply embedded in warts, discs round, flat, black but appearing whitish owing to thick pruine hiding them, exciple thick, uneven, complex, pruinose, whitish. Ascii 1-spored. Ascospores narrowly fusiform, thick walls to 4-5 µm, large, 100-300 x 50-100 µm. Thallus C-, K+ yellow > red, KC+ yellow > yellow-red, Pd+ yellow to orange. On exposed well-lit and sunny rocks of the seashore and inland on rocky ridges. See a particularly characteristic form that occurs on horizontal rock surfaces (granite) of the aerohaline zone: Lepra monogona forme sur surface rocheuse horizontale..

N.B. Probably a fertile morph without soredia of Lepra excludens which is much more common.