Myriolecis dispersa (Pers.) Sliwa, Zhao Xin & Lumbsch

    Thallus crustose, thin or evanescent, minutely granulose, whitish, pale greyish. Apothecia sessile, numerous, isolated or scattered and regular or in dense clusters and then distorted by the compression, 0.2-1 mm diam., disc flat, seldom powdery and only when young, colour highly variable: pale brown-pink, brown-olivaceous, grey-greenish, brownish, greenish... exciple determinate, thick, more or less crenulate or flexuous, white. Epithecium densely strewed with granules insoluble in KOH. Utriform ascus, 42-50 x 15-18 according to our measurements. Ascospores simple, ellipsoid, 8-14 x 4-7 µm according to literature, 10-14 x 5-7 µm according to our measurements. Photobiont: Trebouxia. Chemical spot tests negative except sometimes on apothecia exciple, which is Pd+ orange. Not especially maritime, common on a large range of calcareous  or near neutral substrata, also on old walls of harbour facilities near the seashore, notably dirty ones. Highly tolerant to pollution ; easily mistaken with many other species growing near the seashore. N.B. This species is highly variable and should be clearly distinguished from other species of the 'dispersa' group, notably from (i) Myriolecis (Lecanora) semipallida = flotowiana of which the thallus is darker and with different apothecia: discs pale brown sometimes spotted with blue, exciple K+ yellow,  from (ii) Myriolecis (Lecanora) invadens of which apothecia discs are lead-grey, possibly conspecific to  Myriolecis (Lecanora) semipallida, (iii) from  Lecanora antiqua growing on old granite walls turned into alkaline surfaces owing to mortar leaching and with exciple C+ golden yellow, discs C+ brown-orange, and (iv) from Myriolecis (Lecanora) albescens. N.B. This species, as well as those belonging to the same group, presents a strong  tendency to be parasitic or to grow close to other crustose lichens on hard limestone.*