Verrucaria fusconigrescens Nyl.

   Thallus crustose, rather thin around 0.1 mm thick, non-gelatinous even when wet, areolate, areoles plane to gently convex, edges of areoles lightly browned, not pruinose, rather glossy, brown, dark brown to brown-blackish, prothallus dark brown visible between the areoles. Perithecia immersed in the thallus, but forming low to moderate projections 0.15-0.4 mm diam., seldom slightly prominent, ostiole hardly visible, apex spherical, black. Ascospores simple, oblong-ellipsoid,  20-24 x 7-10 µm. In xeric supralittoral zone spreading to the aerohaline zone on siliceous rocks, aspect rather variable according to exposition. Clearly distinct from Verrucaria (Hydropunctaria) maura that is much blacker (they can thrive together in the lower part of the xeric supralittoral zone)  and from  Verrucaria nigrescens that is calcicolous and grows only on calcareous rocks and cement of walls and is matt, dull black. On calcareous or alkaline rocks, on mortar of walls, see also Verrucaria viridula.*