Dirina fallax De Not. forma fallax Taxon méditerranéen

     Thallus crustose, fairly thick, well demarcated, cracked to areolate, whitish dirty, pale brownish, often blackish by an invasion of cyanobacteria. Apothecia usually numerous, at first globular and closed, then spreading, 1-3 mm in diameter, disc flat, blackish but appearing greyish under a strong pruina, thalline rim thick, sinuous and even sometimes deformed, concolorous to the thallus. Spores fusiform, hyaline, 3-septate, 20-24 x 4-6 µm. Photobiont: Trentepohlia.  Thallus: C + red a little carmine, KC + red a little carmine, K-, P-. Mediterranean taxon occuring on the vertical walls of siliceous rocks (often under sheltered overhangs) by the sea.