Summary:
Features include 1) resupinate growth on barked and barkless hardwood, 2) fruitbodies that are wax-like, subgelatinous, semitranslucent to grayish or with a tint of lilac or blue, generally with scattered to crowded brush-like teeth up to 0.03cm long, 3) spores that are short-cylindric to somewhat curved, smooth, inamyloid, and colorless, 4) cystidia of 2 types: a) thick-walled, conic, encrusted, and b) hyphal ends obtuse, septate, encrusted, and 5) a monomitic hyphal system, the hyphal septa without clamp connections, the basal hyphae easily observed and thin-walled, and the subhymenial hyphae indistinct in a dense layer. Ginns(5) synonymizes Scopuloides hydnoides (Cooke & Massee) Hjortstam & Ryvarden with Scopuloides rimosa (Cooke) Julich and lists the distribution for the latter; however, later Ginns(23) says that one species of Scopuloides, being Scopuloides hydnoides (Cooke & Massee) Hjortstam & Ryvarden), occurs in North America [other species have been described since that publication]; other authors maintain Scopuloides hydnoides separate from Scopuloides rimosa, including Eriksson(7) "microscopically they are quite similar, though slightly different in spore-size, they differ considerably in outer appearance. The aculei of P. rimosa [italicized] are typically cylindrical and scattered over the hymenium, not crowded and penicillate as in P. hydnoides [italicized]"; the online Species Fungorum, accessed August 10, 2005 and August 23, 2020, maintained two species.

Microscopic:
SPORES 3.5-4 x 1.5-2 microns (according to Burdsall 1985 4.5-5 x 2-2.5 microns), elliptic, flattened on one side or slightly concave, smooth, inamyloid, colorless, some with droplets; BASIDIA 4-spored, 10-15 x 3.5-5 microns, cylindric-clavate, without basal clamp connection; CYSTIDIA of 2 types 1) lamprocystidia conic, "smooth when young, later strongly incrusted, rarely with 1 septum, thick-walled", 40-70 x 4-9 microns, and 2) septocystidia cylindric, "blunt, multiply septate, thick-walled, incrusted", projecting beyond the basidia, up to 100 x 10 microns; HYPHAE monomitic, 3.5-8 microns wide, tightly interwoven, short-celled, thin-walled to thick-walled, septa without clamp connections, (Breitenbach), SPORES 3.5-4(5) x 1.8-2(2.2) microns, short-allantoid, smooth, thin-walled; BASIDIA in a dense palisade, 4-spored, 12-15 x 3.5-4.5 microns, subclavate, thin-walled or basally thickened, without basal clamp connection; CYSTIDIA (metuloids, lamprocystidia) about 40-60 x 8-12 microns, often projecting 10-30 microns beyond the basidia, basally thick-walled, conic or more rarely obtuse, strongly encrusted, hyphal ends present, "especially in the top of the hymenial aculei, usually projecting 20-50 microns or more, septate and strongly incrusted"; HYPHAE monomitic, without clamp connections; "subhymenium with densely interwoven hyphae"; subiculum "as a rule very thin and composed of relatively long-celled hyphae", arranged in parallel fashion next to the substrate, with somewhat thickened walls, 4-7 microns wide, (Eriksson), SPORES "generally suballantoid to short cylindric, smooth and thin-walled, 4.5-5 x 2-2.5 microns", inamyloid; BASIDIA 4-spored, small, about 8-12 x 3-5 microns; CYSTIDIA numerous, about 50-70 microns long and 10 microns wide at base, conic, "thick-walled and strongly encrusted, sometimes lateral, especially in young fruitbodies"; hyphal ends present in most specimens, obtuse, projecting, as a rule septate, and strongly encrusted; HYPHAE monomitic, basal hyphae easily observed, 3-4 microns wide, thin-walled, without clamp connections, subhymenial hyphae indistinct and forming a dense layer, (Hjortstam)

Notes:
Scopuloides hydnoides has been found in BC, NS, ON, AL, AZ, DC, FL, GA, IA, IL, LA, MI, MN, NC, NY, PA, TN, VT, and WI, (Ginns(5), who synonymizes Scopuloides hydnoides with Scopuloides rimosa and lists the distribution for the latter).

Synonyms and Alternate Names:
Odontia hydnoides (Cooke & Massee) Hoehn.
Peniophora hydnoides Cooke & Massee
Phlebia hydnoides (Cooke & Massee) M.P. Christ.