Thallus formed by hyphae immersed in the substrate and very inconspicuous except for its color different from the wood, greyish-white, pale greyish, sometimes with small brownish goniocysts in places. Apothecia numerous, ovoid to linear, arranged parallel to each other, 1-2.5 x 0.2-0.3 µm, arising under the surface of the wood then spreading the fibers of the wood which they shatter to take on a " buttonhole "with tapered ends, rough disc, slightly convex brownish at the beginning then black, thin margin hardly visible giving the impression of a lirelle to the whole which in the dilapidated state can disappear leaving a grayish scar. Spores simple, elliptical, 11-16 x 5-8 µm. Colored chemical reactions generally negative, sometimes K +/- yellow, P +/- yellow. In the mountains on decorticated wood or the stumps of conifers but sometimes at the seaside on rotting damp worked wood, in particular the wrecks of wooden boats.
