Catillaria chalybeia (Borrer) Massal var. chalybeia
Thallus crustose, 2-5 cm diam., often mosaic-forming, variable according to rock properties, thin and evanescent, cracked or rimose to verrucose areolate, with areoles c. 0.1-0.4 mm diam., grey, grey-green olivaceous to grey-black sometimes with matt or glossy steel-blue and typically all the colours of copper oxydes; prothallus distinct, blackish tinged with steel-blue. Apothecia small, sessile, scattered all over the thallus, 0,2-0,8 mm, mostly flat, sometimes becoming convex, rather glossy, brown-black to black; proper margin thin, usually concolorous with disc but sometimes sligthly greenish. Ascii 8-spored with paraphyses forming a black outer coat at apices. Ascospores 1-septate, oblong, 8-12 x 3-4 µm according to literature, (7) 8-10 x 3-4 µm according to our measures. Photobiont: Myrmecia. Chemical spot tests negative. Not especially maritime, on nutrient-rich rocks of the supralittoral or aerohaline zones or on weakly acidic or alkaline walls. N.B. There are many similar species in this zone and generally a microscopic observation is required in order to make a proper identification. N.B. Highly variable species -or cluster of species- including several taxa among which many are maritime. See Catillaria atomarioides with smaller apothecia and ascospores, Catillaria subviridis strictly maritime with larger apothecia and Catillaria lenticularis with a brownish thallus and restricted to calcareous substrata.