Acarospora fuscata (Nyl.) Arnold

     Thallus areolate-squamulose, wide spreading and often forming extensive patches, rarely scattered; areoles 1-3 mm wide, very variable, mostly contiguous to each others, irregular in shape, flat, at times sub-lobulate or weakly imbricate (crushed flower-like), surface uneven, irregular, pale to dark red, brown-red ochre or yellow-brown, often with black margins. Apothecia 0.2-1 mm diam., mostly 1 per areole but  possibly 1-5) per areole, at first punctiform, later concave or flat, usually angular or irregular, immersed, or very slightly protruding, disk red-brown to black, usually darker than the thallus, making easy to locate reproductive bodies. Ascus in club-shape, 130 x 30 µm according to our mesurements. Simple, narrowly ellipsoid, somewhat cylindrical spores, 4-6 x 1-1.5 µm according to the literature, 4-6 x 1-1.5 (2) according to our measurements.  Photobiont: Chlorococcales. Thallus: C+ red, K- , KC+ red, Pd-. Nitrophilic, not especially maritime species but often found on nutrient-enriched siliceous bird-perching rocks mainly inland.

N.B. Seems to be more or less parasite, at least during early life, of other nitrophilic saxicolous lichens. 

Cf. Acarospora impressula with unlobate areoles and displaying negative chemical reactions and most often coastal in our prospection area, and Acarospora subrufula strictly costal and  K+ red-wine.

N.B. Sometimes parasitized by Stigmidium fuscatae.