Ionaspis lacustris (With.) Lutzoni

    Thallus crustose, rather thick, 0.2-0.5 mm, smooth to slightly rimose or cracked, potentially forming mosaics, brown-orange, cream-orange, prothallus brown-redish, sometimes absent. Apothecia usually numerous, scattered, immersed at first, then more or less sessile, rounded to angular, the oldest to 0.1-0.5 mm diam., disc concave then flat, orange, pink-orange, transluscent when moist (apricot jam-like) exciple distinct, paler, concolourous to thallus. Ascospores simple, broadly ellipsoid, colourless, 13-20 x 6-11 µm. Photobiont: Trebouxia. Chemical spot tests negative. On siliceous rocks immersed or just above the mean water level of lakes and rivers, subjected to periodical immersion during floods. N.B. Ionaspis ceracea differs only by its habitat, on humid vertical and humid schist walls exposed to the North, far from streams, rivers or springs.*