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Remarks (internal):This is the first report of this species from North America. The species is rare in Eurasia and thus far has only been found on Sphagnum in bogs.
Singer (1943 l.c.) described it from Artubasz (Artybash), Siberia, and indicated that the pileus was depressed centrally. Favre (1948 l.c.) described it as Omphalia cincta from the Alps and noted that a conspicuous umbo was present on most basidiomes. Singer (Zeit. f. Pilzk. 19: 1-4. 1955) later suggested that Clitocybe brevibasidiata and Omphalia cincta were synonymous. This prompted Favre (Res. recherch. sci. entrepr. Parc Nat. Suisse 6(N.S.): 416. 1960) to argue that they differed in their pileus shape and basidial sizes. His arguments appeared to have been accepted by Singer (1964 l.c.) who tentatively recognized both species, however Singer & Clémençon (Nova Hedw. 23: 321-322. 1972) have since placed O. cincta in synonymy with Gerronema brevibasidiatum based on their studies of the type and paratypes of the former.
The holotypes of both C. brevibasidiata Singer and O. cincta Favre and the paratypes cited by Singer & Clémençon (1972 l.c.) were acquired and compared. There are no appreciable differences between the various collections microscopically (Figs. 4-9) or macroscopically and therefore Singer's synonymy is accepted. The North American collection was slightly paler. The collection was made in an open site and possibly was faded or washed out by rain. The species normally has more yellowish pigments in the pileus and stipe. It is also abnormal for the variation in sterigmata number and sizes of basidia.
In addition to the reports by Favre and Singer, Omphalina brevibasidiata has been recorded from the Tatra mountains in Czechoslovakia (Kubicka, Ceská Mykol. 10: 159-161. 1956) and from northern Sweden near Abisko (Lundell and Nannfeldt, Fungi Exsic. Suecici 2908, specimen in DAOM examined) .
Omphalina brevibasidiata is distinguished from other Omphalinas by its normally papillate, yellowish pileus, sphagnicolous habitat, the presence of clamp connections and nonincrusting pigments, and small, not necessarily short, basidia, under 5.5 µm diam. usually.
Description type:Non-original description 
Description:Omphalina brevibasidiata (Singer) Singer, Lilloa 22: 212. 1951.
= Clitocybe brevibasidiata Singer, Ann. Mycol. 41: 45-46. 1943.
= Gerronema brevibasidiatum (Singer) Singer, Sydowia 15: 51. 1961.
= Omphalia cincta Favre, Beitr. Kryptogam. Schw. 10: 64, 212. 1948.
= Gerronema cinctum (Favre) Singer, Nova Hedw. 7: 80. 1964.
Pileus: 9-11 mm wide, convex with a small prominent umbo or depressed, translucent-striate, moist, glabrous; disc area umber to pale umber, otherwise white to very pale straw; margin straight and slightly dentate; context concolorous; odor and taste not distinctive. Lamellae: adnate to uncinate, white, moderately broad, subdistant; 2 tiers of lamellulae. Stipe: 30-33 mm long, 1-1.5 mm wide above, equal or slightly clavate below, fistulose, cartilaginous, polished, white, flexulose and slightly puckered; base strigose; fibrils white. Pileipellis: hyphae repent, thin-walled, smooth, non-inflated, hyaline, clamped, embedded in an indistinct gelatinous matrix, 2-5.5 µm diam. Pileus trama: hyphae slightly interwoven, hyaline, smooth, thin-walled, most inflated and constricted at septa, clamped, 3-12.5 µm diam. Lamellar trama: hyphae similar to above, more or less parallel, inflated or not, 2-14 µm diam.; oleiferous hyphae scattered; subhymenium not distinctive. Basidia: elongate-clavate to nearly cylindrical-capitate, (1-)2-, 4-(5-) spored or with irregular sterigimatalike growth, hyaline, thin-walled, clamped, 22-28(-35) x 4-5.5 µm. Basidiospores: 5.5-8.4 x 3-4.5 µm, smooth, hyaline, thin-walled, nonamyloid, elongate ellipsoid to short ellipsoid, rarely ovoid or obpyriform, inequilateral; apiculus prominent. Stipe Trama and Taulopellis: similar, hyphae parallel, thin-walled, smooth, hyaline, clamped, most noninflated, 1.5-12 µm diam.; hyphal ends occasionally projecting near stipe apex but not well differentiated into cystidia. Basal mycelium: hyphae mostly aggregated into strands, noninflated, hyaline, smooth, thin-walled, clamped, 2-4 µm diam.
Substrate: scattered on Sphagnum mixed with other bryophytes on a compact hummock in an open bog site.
Distribution: Quebec.
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