Acarospora privigna (Ach.) A. Schneid.

=Polysporina simplex (Davies) Vezda

   Thallus insignificant and most often evanescent and inconspicuous, pale gray, pale greenish-gray, olive. Apothecia more or less submerged or sessile, often distorted by compression, 0.2-0.8 mm in diameter, scattered or in groups but most often in small fractures of the rock which makes them take for black mica on the granite, rough or umbonnated disc, rounded, black or black-reddish, crenellated margin which can come on the disc and give it a gyrous appearence, black. Utriform asci containing a hundred spores, 50-80 x 15-30 µm according to our measurements. Spores tiny, narrowly elliptical, 3-5 x 1-1.5 µm. Branched paraphyses. No characteristic chemical reactions. Photobiont: Chlorococcaceae. Species occurring on rough, acidic or weakly calcareous rocks of the xeric supralittoral zone but also inland (probably different taxon).

N.B. On very exposed sea cliffs and in this case watch out for Trimmatothelopsis versipellis of similar appearance but whose apothecia are less deformed and not gyrous.

N.B. This taxon is better known under the name of Polysporina simplex which was less likely to lead to confusion, the epithet of privigna having been used to designate many taxa...

N.B. There is a group of taxa very similar to Polysporina simplex which are parasitic on crustose lichens, at least initially, see Polysporina canasiacensis Cf. and its forms, name provisionally adopted. These parasitic forms appear to be devoid of algae.