Type:— DR CONGO. Shaba Province, Kipopo, 10 January 1961, M. C. Schmitz–Levecq 315 (BR 11476–30).

Description:— Pileus 6–16 mm diam, plano-convex to umbonate, with a dark brown papilla; margin striate; surface dry, glabrous; dark orangish brown to orange (6 B –D6–8). Context thin, light brown (6 B 3). Lamellae adnate, close with 6 series of lamellulae, narrow (0.7–1.5 mm), cream (5 A 2), non-marginate. Stipe 16–50 × 1–2 mm diam, central, cylindrical, hollow; surface pruinose; apex orangish white (5 A 3–4), centrally yellow (5 B 6), base orangish brown to brown (6D6–8). Odor and taste not distinctive.

Basidiospores 7.2–8.8 × 3.2–4.8 μm [x m = 7.79 ± 0.48 × 3.99 ± 0.38 μm; Q = 1.67–2.50; Q m = 1.97 ± 0.21, n = 25, s = 1], ellipsoid, smooth, hyaline, inamyloid, thin-walled. Basidia 16–23.2 × 7.2 μm, clavate, 4-spored, hyaline, inamyloid, thin-walled; sterigmata 2.4–4.8 × 0.8–1.6 μm. Basidioles 13.6–24.8 × 4–5.6 μm, clavate, hyaline, inamyloid, thin-walled. Cheilocystidia abundant, of Siccus - type broom cells; main body 9.6–23.2 × 4.8–7.2 μm, clavate or irregular, seldom 2-lobed, hyaline, inamyloid, apically thick-walled; apical setulae 3.2–8.8 × 0.8–1.6 μm, cylindrical to conical, seldom branched, light yellowish brown, inamyloid, thick-walled. Pleurocystidia absent. Pileipellis mottled, a hymeniform layer of Siccus- type broom cells; main body 8–15.2 × 7.2–8 μm, clavate or irregular, seldom 2-lobed, hyaline, inamyloid, thin-walled; apical setulae 2.4–20 × 0.8–1.6 μm, 7–9 setulae per cell, cylindrical to conical, light yellowish brown, inamyloid, thick-walled. Pileus trama interwoven; hyphae 1.6–12.8 μm diam, cylindrical to inflated, smooth, hyaline, strongly dextrinoid, thin-walled. Lamellar trama regular; hyphae 3.2–6.4 μm diam, cylindrical to inflated, smooth, hyaline, strongly dextrinoid, thin-walled. Stipe tissue monomitic; cortical hyphae 4–9.6 μm diam, parallel, cylindrical, smooth, hyaline, dextrinoid, thick-walled; medullary hyphae 3.2–14.4 μm diam, parallel, cylindrical to inflated, smooth, hyaline, dextrinoid, thin-walled. Caulocystidia of two types; 1) scattered Siccus- type broom cells; main body 10.4–20 × 5.6–7.2 μm, clavate or irregular, seldom lobed, hyaline, inamyloid, thin-walled; apical setulae 0.8–14.4 × 0.8–2.4 μm, cylindrical to conical, seldom branched, hyaline, inamyloid, thick-walled; 2) smooth non-setulose cystidia with main body 20.8–48 × 7.2–11.2 μm, clavate to cylindrical or irregular, smooth, hyaline, inamyloid, thick-walled. Clamp connections present.

Habit, habitat and known distribution:—Solitary or in small clusters on wood and leaf litter of undetermined trees. Africa (Benin, DR Congo, Kenya, Malawi, Nigeria, Tanzania, Uganda), Madagascar.

Material examined:— MADAGASCAR. Region Analamanga, District Ankazobe, Commune Ambatoharanama, Ambohitantely Forest Reserve, Sentier Botanique, elev. 1574 m, GPS: 18˚ 11.504’ S, 47˚ 17.074’ E, 6 February 2014, J. E. Shay 227 (SFSU).

Notes:— Marasmius katangensis has a centrally rugulose, dark orangish brown pileus with orange margin, close lamellae, a pruinose stipe with two types of caulocystidia, relatively small basidiospores with mean 7.8 × 4.0 μm, no pleurocystidia, and no setae. Morphologically, the species is similar to M. corrugatiformis, but the latter has cheilocystidia of two types, and caulocystidia of only one type (non-setulose, cylindrical to clavate). JES 227, determined here as M. katangensis, is easily confused with Madagascar material determined by Antonín & Buyck (2006) as M. corrugatiformis (KX 148981), but ITS sequences clearly distinguish the two (Fig. 1a).

Based solely on ITS data, JES 227 (KX 148991) is basal to a clade containing M. occultatiformis Antonín, Ryoo & H.D. Shin, described from Korea on detritus of Acer and Juglans. Morphologically, JES 227 is very similar to M. occultatiformis, differing primarily in the latter species having a glabrous stipe lacking caulocystidia; other features are indistinguishable.