Myriolecis albescens (Hoffm.) Sliwa, Zhao Xin & Lumbsch forme sur roche calcaire.

     Thallus fairly thick, crustose, compact or formed of smaller but neighboring thalli, sometimes giving the impression of being lobed at the margin, cracked to areolated, areolas a little rounded or swollen, chalk white, dirty white. Apothecia very numerous in compact groups on the thallus which they can cover entirely, sessile and protruding but sometimes, especially at the beginning, a little submerged in the thallus, 0.5-2 mm, flat disc, sometimes a little convex if old or concave so moist, pale pinkish-brown, light brown so dry, but most often so moist with an opaline or alabaster appearance: gray, grayish-greenish, celadon, cream, etc. sometimes a little pruinose in white, abundant margin very clear and very visible, erect, sinuous to a little crenate, white or concolorous with the thallus. Utriform asci, 45-50 x 15-20 µm according to our measurements. Simple spores, largely elliptical, 8-15 x 4-6 µm according to the literature, 9-12 x 4-5 according to our measurements. Photobiont: Trebouxia. C-, K-, KC-, P- but sometimes margin of apothecia P + orange, UV- or sometimes apothecia UV + green. Species very variable according to its substrate and its habitat, very nitrophilic and resistant to pollution, not especially maritime, but which seems to have maritime taxa, coming most often on calcareous or slightly acidic sunny rocks but also on old walls, the concrete and particularly by the sea on old blockhaus, sometimes on fiber cement, which is rarer on bark, wood, artificial substrates. N.B. Easy to confuse with Myriolecis (Lecanora) dispersa grp. with a smaller thallus, greyish or blackish and with more dispersed apothecia, also with Myriolecis (Lecanora)  bandolensis thermophilic maritime species coming on much rarer limestone rocks whose apothecia discs are strongly stained with more or less dark green and which are not translucent in humid weather and also with Lecanora salina with smaller apothecia and which comes in the area of ​​Hydropunctaria (Verrucaria) maura. N.B. Apothecia sometimes parasitized by Arthonia apotheciorum they then turn black.