Summary:
Features include 1) resupinate growth on conifer wood, 2) a whitish surface with teeth up to 0.1cm long, 3) tough consistency, 4) spores that are allantoid, smooth, and inamyloid, 5) basidia in candelabra form, 6) cylindric hyphae in a tuft at the tips of the teeth, and 7) a monomitic hyphal system, the hyphae thick-walled without clamp connections. Note that the Gilbertson(11) description says "The allantoid spores, abundant cystidia, and simple-septate hyphae distinguish this species", but Eriksson(5) says there are no cystidia (probably regarding the abundant cystidia at the tips of the teeth as hyphal ends), and that "There should be no problem recognizing O. romellii [name italicized] thanks to its tough consistency, its afibulate, thickwalled hyphae and its allantoid spores".

Microscopic:
SPORES 4-4.5 x 1.2-1.5 microns, allantoid - suballantoid, smooth, inamyloid, acyanophilic, thin-walled; BASIDIA 4-spored, 12-15(20) x 4-5 microns, subclavate then subcylindric, often with slight median constriction, walls thin but thickening in basal half and upper limit of thicker layer sometimes visible; CYSTIDIA none; HYPHAE monomitic: hyphae of the spines 4-5 microns wide, straight, parallel, thick-walled, with numerous constrictions and septa but no clamp connections, apically thin-walled "and with rounded and obtuse apices", "hyphae of the subiculum besides with thinwalled, narrower (2.5-3 microns) hyphae", generative hyphal branches 2-3 microns wide, thin-walled, "richly branched and in older parts of the fruitbodies forming a subhymenium of densely interwoven hyphae"; all hyphae inamyloid and acyanophilic, (Eriksson), SPORES 4-5 x 1-1.5 microns, allantoid, smooth, colorless; basidia 4-spored, 4-5 microns wide, clavate, in distinct candelabra; CYSTIDIA in tufts at tips of teeth, projecting up to 30 microns, 4-5 microns wide, thick-walled at the base, the wall gradually thinning out toward the tip; HYPHAE in the core of each tooth with a distinct parallel arrangement, continuing to form the tuft of cystidia at the tip of the tooth; SUBICULAR HYPHAE 3-5 microns wide, colorless, moderately thick-walled, often with slight constrictions, irregular in outline, with frequent branching, simple-septate, (Gilbertson)

Notes:
Odonticium romellii has been found in BC, WA, ID, AB, MT, and NC, (Ginns). It is rare in northern Scandinavia (Finland, Norway, and Sweden) (Eriksson).