Summary:
Features include 1) resupinate growth, or partly with a cap, on conifer wood, 2) a texture that is leathery to woody, 3) the cap when present brown, deeply and sharply and concentrically sulcate, often with tinder-like tomentum, especially when young, 4) a spore-bearing surface that is light yellow with a salmon tint, turning reddish where bruised, smooth becoming tuberculate or concentrically sulcate, 5) in a section of the cap, an uppermost tinder-like layer, separated from the layer corresponding to the subiculum by a thin, resinous, hard layer visible as a dark line, 6) spores that are round or nearly round, echinulate, and amyloid, with somewhat thickened walls, 7) cystidia that are conic and encrusted in their upper part, the lower part yellowish and tapering to bearing hyphae, and 8) a trimitic hyphal system, the septate hyphae with clamp connections.

Microscopic:
SPORES 5.5-6.5 x 5 microns, round or nearly round, echinulate, with somewhat thickened walls, amyloid; BASIDIA 4-spored, 25-35 x 4-5 microns, clavate, with basal clamp connection; CYSTIDIA "numerous, thickwalled, apically conical, encrusted, basal part tapering to the bearing hyphae, somewhat pigmented, yellowish or pale ochraceous in the proximal part, total length 40 - 65 microns, encrusted part 20 - 30 microns, greatest width 8 - 10 microns", inner structure somewhat unclear, seeming to consist of 2 parts, "a proximal pigmented part, evidently formed by thickening of the wall", and a distal part that in old cystidia is as a rule colorless; HYPHAE trimitic: 1) skeletal hyphae, 2.5-4 microns wide, thick-walled, straight, with sparse septa and clamp connections, 2) binding hyphae, 2-3 microns wide, thick-walled, richly branched, and 3) generative hyphae, 2-3 microns, thin-walled, richly branched, with clamp connections, "with some adventitious septa", "the upper tinder-layer consists mainly of brown skeletal hyphae, the subiculum of hyaline or pale yellowish, thickwalled, horizontal skeletals with numerous binding hyphae between them, as well as few generative hyphae, at least in young specimens; subhymenium of vertical skeletals, irregular binding hyphae, generative hyphae, cystidia, and old, shrunken basidia", (Eriksson), spores white in spore collection, (Burt)

Notes:
Laurilia sulcata has been found in BC, WA, OR, ID, AB, ON, PQ, AK, CO, LA, MI, MT, NC, NH, NY, PA, TN, TX, UT, VT, WI, and WV, (Ginns). It has also been found in Norway, Sweden, and Finland, (Eriksson).

Synonyms and Alternate Names:
Anthostoma diathrauston (Rehm) Cooke
Fuckelia diathrauston (Rehm) Cooke