Description: Thallus crustose, episubstratic, clearly lichenized, usually rather thick, continuous or finely rimose, whitish, without a distinct prothallus. Apothecia arthonioid, immarginate, black but sometimes white-pruinose, irregularly rounded, stellate or elongate and more or less branched, 0.1-0.3(-0.5) x 0.3-1.5(-2) mm, level with thallus. Proper exciple poorly developed; epithecium olivaceous brown, 10-15 μm high, K+ olive-green; hymenium colourless, c. 40-60 μm high, I+ blue turning blood-red, K/I+ blue; paraphysoids anastomosing, branched in upper part, c. 1 μm thick; hypothecium colourless to pale brown, 10-20 μm high. Asci 8-spored, broadly clavate to subglobose, semi-fissitunicate, with a large apical dome, a distinct ocular chamber, and a K/I+ bluish ring-structure, Arthonia-type. Ascospores submuriform to muriform, with 6-8 transverse and 1-2 longitudinal septa in each transverse segment, persistently hyaline, obovoid to ellipsoid, (23-)26-30(-33) x (9-)10-13 μm, always with a distinct, gelatinous, I+ red sheath. Pycnidia very rare, more or less hemispherical, black-brown. Conidia bacilliform, straight or slightly curved, (4-)5-7 x 1-1-5 μm. Photobiont chlorococcoid, small-celled. Spot tests: thallus K-, C-, KC-, P-. Chemistry: without lichen substances.
Note: apparently not rare along the eastern coast of the Iberian Peninsula, especially on conifers, this species should be looked for also in Italy.