Summary:
Features include 1) resupinate growth on wood or humus, 2) a mould-like, continuous fruitbody that is avellaneous to wood brown, smooth to deeply fissured, with a darker subiculum, and a fringed to fibrillose margin that is paler than the spore-bearing area, 3) spores that are irregularly roundish to lobed, spiny, and with yellowish brown to pale brown walls, 4) basidia often with transverse septa, and 5) hyphae with clamp connections.

Microscopic:
SPORES 8-10 microns in diameter, irregularly subglobose [nearly round] to lobed, often elongated along one axis, echinulate, walls yellowish brown to pale brown; BASIDIA 4-spored, 50-70 x 9-14 microns, "stout-clavate, somewhat attenuated at the base", with clamp connection at base, often with transverse septa; SUBHYMENIAL HYPHAE 3.5-5(6) microns wide, wall thickening apparent, colorless, with clamp connections; SUBICULAR HYPHAE 4-6(7) microns wide, pale yellowish brown, wall thickening apparent, septa with frequent clamp connections; CORDONS 15-75 microns wide, "pale yellowish brown to dark brown, branched", individual hyphae 3-3.5 microns, pale yellowish brown, wall thickening apparent, with clamp connections, (Larsen)

Notes:
Tomentella avellanea has been found in BC, WA, ON, AZ, CA, NY, and TX, (Ginns), as well as France and the United Kingdom, (Larsen).