Summary:
Features include 1) resupinate growth on bark or less commonly barkless wood, 2) fruitbodies that start circular but become confluent, white when young becoming cream to bright yellow or ocher-yellow, waxy-membranaceous in consistency, smooth at first but developing teeth that are cylindric to conic to plate-like, 3) spores that are smooth, inamyloid, colorless, and cylindric to slightly curved, 4) basidia that are 4-spored and often constricted, 5) leptocystidia (?cystidioles) that are present but rarely projecting, sometimes moniliform, and 6) a hyphal system that is monomitic with clamp connections.

Microscopic:
SPORES 8.0-13.2 x 2.6-4.0 microns, cylindric, flattened on one side, sometimes slightly curved, smooth, inamyloid, colorless; BASIDIA 4-spored, 26-33 x 4.6-6.6 microns, at first ovoid, elongating to clavate, usually with a central constriction; GLOEOCYSTIDIA 35-60(85) x 5.2-7.2 microns, rarely projecting, thin-walled, with homogeneous content staining in phloxine, negative with sulfobenzaldehyde, "indistinguishable from immature basidia in hymenium developing at the margin of fruit bodies", "but soon recognizable as they elongate between the spent basidia", clavate or cylindric, often with constrictions, flexuous [wavy]; in section thin at first, consisting of a few hyphae radiating over substrate and curving down to form hymenium, "becoming 200-800 microns or more thick with teeth up to 1500 microns or more long, with a thin basal layer of horizontal hyphae, a broad intermediate layer making up most of the thickness of the section, composed of loosely arranged, obliquely or vertically descending hyphae", and often containing masses of crystalline material, hyphae 2.0-4.0 microns wide, uniform throughout, loosely arranged, "thin-walled, nodose-septate, often lightly incrusted with crystals", with frequent H-anastomoses; moniliform terminal cells only on vegetative mycelium at base of fruitbody "or in growing margin or on hyphae in decayed wood", (15)30-66 microns long, 3.3-4.6 microns wide at base, slender, tapering, flexuous [wavy], (Nobles), SPORES 9-11 x 3-3.5 microns, allantoid, smooth, inamyloid, thin-walled, with homogeneous contents; BASIDIA 4-spored, 20-25 x 4-6 microns, subclavate to subcylindric (often constricted), with basal clamp connection; CYSTIDIA generally few, especially when mature, 50-70 x 5-8 microns, thin-walled, with homogeneous contents, cylindric with few constrictions to definitely moniliform; HYPHAE monomitic mostly 3-4 microns wide, "thin-walled or in the centre of the teeth with somewhat thickened walls", densely branched and closely interwoven in the subhymenial part, "otherwise rather straight with sparse branches", all septa with clamp connections, (Eriksson), SPORES 8.5-10 x 3-3.5 microns; LEPTOCYSTIDIA 45-60 x 5-7 microns, sinuous to moniliform, (Breitenbach), SPORES 7-11 x 2.3-3 microns, with small apiculus; CYSTIDIA and gloeocystidia lacking but moniliform CYSTIDIOLES sometimes present, 35-60 x 5-7 microns; BASAL HYPHAE distinct and straight, SUBHYMENIAL HYPHAE often tortuous-torulose and indistinct, (Julich)

Notes:
Basidioradulum radula is found in BC, WA, ID, NB, NF, NS, ON, PE, PQ, CA, DC, FL, GA, IA, IL, KY, LA, MA, MD, MI, MO, MN, MS, NC, NE, NH, NJ, NY, OH, PA, RI, TX, VT, WI, and WV, (Ginns). It is common in most parts of Scandinavia and Finland, (Eriksson). It occurs in Europe including Switzerland, and in Asia, (Breitenbach). It is found in Finland, Germany, Netherlands, Sweden, and the United Kingdom, (Julich).

Synonyms and Alternate Names:
Corticium colliculosum Berk. & M.A. Curtis
Corticium hydnans (Schwein.) Burt
Hydnum radula Fr.
Hyphoderma radula (Fr.) Donk
Hypomyces cervinus Tul. & C. Tul. Select. fung.
Radulum bennettii Berk. & M.A. Curtis
Radulum orbiculare Grev.: Fr.