Trimmatothelopsis versipellis (Nyl.) Zsckacke

    Thallus squamulose, squamules verrucose, scattered or in small clusters, deeply encrusted within the holes of the rugged rock surfaces, 0.5-2 mm tall, 1-10 mm across, verrucose at first, more or less conical, then almost completely covered by apothecia when mature, blackish. Apothecia 0.5-1 mm diam., 1 to 4 per squamule, initially embedded in squamulose warts, then opening and showing  the discs, more or less distorted, concave to flat, smooth or slightly granular, sometimes with brown-blackish umbo, exciple thick, blackish. Ascii 200-300-spored, 100-150 x 15-30 µm. Ascospores oblong, 3-4 x 1,5-2 µm. Chemical spot tests negative. Restricted to a small number of habitats, but locally abundant, on rough granite rocks of highly exposed walls and cliffs of the foreshore, most often together with Polysporina simplex  which then is easily mistaken, but it is the parasitic forms of Polysporina canasiacensis, which are the most similar.

N.B. Critical taxon which is the subject of many discussions ...