Lecanora ochroidea (Ach.) Nyl.
Thallus crustose, minutely and regularly cracked and areolate, areoles distinct, granulose, whitish, pale grey-ochraceous, ochraceous, ochre-reddish, prothallus white, slightly fimbriate. Apothecia numerous, 0.1-2 mm diam., sessile, disc pale grey-pink, pale beige-pink, more or less convex, dense white-pink pruine, exciple entire, more or less excluded when old, concolourous to the thallus but sometimes darker. Ascospores (but sometimes with an "equatorial belt" colored in certain dyes for microscopy), largely elliptical to ovoid, 10-14 x 6-8.5 µm according to the literature, 10-13 x 6-8 µm according to our measurements. Photobiont: Trebouxia. C-, K+ yellow >red, KC +/- red, Pd+ golden yellow > sometimes orange or red (slow reaction on fresh sample). Rare and localized to sheltered siliceous rocks more or less vertical in the xeric supralittoral zone of capes and heads. N.B. Lecanora subcarnea is very similar, K-, not especially maritime and usually on less acid rocks and sometimes together with Lecanora ochroidea and in that case the K reaction is required to distinguish the two species in the field. Lecanora rupicola is a much more common species and may be confused especially if its apothecia are well-developed, but it grows on more exposed rocks and is C+ yellow. Not to be confused with Lecanora praepostera of which the chemical reactions are similar but with very abundant apothecia, discs dark brown usually not pruinose.