Circinaria hoffmanniana (S. Ekmann & Fröberg ex Sant.) A. Nordin = Aspicilia contorta ssp. hoffmanniana

    Thallus crustose, areolate, formed of flat or more or less convex areoles, angular and irregular, 0.5-1.5 mm wide, arranged contiguously or separated by a slit, grayish, gray-brown, grayish, gray-greenish. Apothecia aspicilloid, 0.2-0.5 irregular and poorly developed, black disc sometimes pruinose whitish, irregular margin more or less raised and striated. Ascospores simple, hyaline, subglobose to globose, 18-28 x 17-26 µm. Pycnidia rare, punctiform, black, conidia filiform, 6-10 x 1 µm. Photobiont: chlorococcoid. K-, C-, KC-, P-. Common species on all basic natural or artificial substrates (concrete, cement, etc.), even in cities because this pioneer species tolerates pollution.

N.B. This highly variable species, interpreted differently by different authors, probably contains several taxa, including:

_ Circinaria hoffmanniana morpho hoffmanniana : a very xeric form found on sunny surfaces, gray-brown, brownish.

_ Circinaria hoffmanniana morpho viridescens: grows in dimly lit and humid areas, gray-greenish.

N.B. Sometimes difficult to separate from Circinaria contorta.