Rhizocarpon geographicum subsp. prospectans (Räs.) Hawksw. & Sowter Cf.

   Thallus crustose up to 10 cm in diameter, yellow, greenish-yellow, very divided and formed of flat angular areoles, these areoles are separated by cracks (sometimes wide) revealing the black hypothallus. Lecidein apothecia appearing in the fissures between the areoles, rounded, 0.5-1.5 mm in diameter, black, disc slightly concave to slightly convex, margin clear. Muriform spores with 6-12 visible cells, colorless but become grayish brown in old age, 20-32 x 9-16 µm. C-, K-, KC-, P-. Atlantic taxon coming on siliceous rocks, at the edge or not very far from the sea.

_ Presented here with the usual reservations because the Rhizocarpon geographicum group is still poorly known and the taxa described are still poorly defined and linked by intermediaries.