Key to the European species of Rhodocybe sect. Rhodocybe 1. Pileipellis with numerous globose elements................. R. praesidentialis Consiglio, Contu, M. Roy, Selosse & Vizzini (2007: 26) ‒ Pileipellis consisting only of cylindrical hyphae without globose or inflated elements....................................................................2 2. Spores subglobose to broadly ellipsoid..............................................................................................................................................3 ‒ Spores ellipsoid to amygdaliform.......................................................................................................................................................4 3. Spores (5‒)5.5‒6.5(‒7.6) × (4.2‒)4.5‒5.5(‒6) μm, Q = 1.16‒1.38, pileus up to 55 mm broad, context unchanging when bruised, lamellae medium crowded, grey to brown.......................................................................................... R. formosa (= R. minutispora) ‒ Spores 5.7‒8 × 4.5‒5.9 μm, Q = 1.1‒1.5, pileus up to 25 mm broad, context darkening to blackish when old or bruised, lamellae quite distant, dark grey............................................................................................................................................. R. griseonigrella 4. Light blue to violaceous tinges present at least at stipe apex and well-developed cylindrical caulocystidia................. R. ardosiaca ‒ Stipe without violaceous tinges and caulocystidia.............................................................................................................................5 5. Basidiomes slender, fragile, conical-convex pileus with argillaceous to pale brown tinges (white in var. virgineopusilla), unpleasant smell and taste (like rotten fish), large spores, 7.5‒10 × 4.5‒5.5 μm....................................................................... R. obtusatula ‒ Basidiomes less fragile, with different smell and smaller spores.......................................................................................................6 6. Pileus at first covered with abundant white pruina (as a micaceous sheen).......................................................................................7 ‒ Pileus without white pruina................................................................................................................................................................9 7. Pileus 6–18 mm broad, conico-convex to conical, with a broad obtuse umbo, bright yellow-brown, dark brown at centre, not cracked, lamellae yellow-brown...................................... Clitopilus djellouliae Contu, Vizzini, P. Roux & Guy Garcia (2011: 158) ‒ Pileus 4–30 mm broad, convex, soon convex-depressed, without umbo, dark grey, greysh- brown, minutely cracked, lamellae grey.....................................................................................................................................................................................................8 8. Pseudocystidia abundant, 40–70 × 6–8 μm......................................................................................................................... R. caelata ‒ Pseudocystidia rare, 30–40 × 3–4 μm.................................................................................................................................... R. dubia 9. Pileus blackish brown, spores, 6.8‒9 × (5.7‒)6.2‒7.5 μm and large basidia, 32‒44 × 9.5‒13.5 μm, pseudocystidia up to 13 μm wide, filled with colourless contents in KOH, and growth in dwarf shrubs in tundra.............................................. R. finnmarchiae ‒ Not as above.....................................................................................................................................................................................10 10. Spores oblong to subfusiform, Q = 1.7‒2.1............................................ Clitopilus marinaensis Vila, Contu & F. Caball. (2009: 9). ‒ Spores ellipsoid or amygdaliform, Q ≤ 1.7......................................................................................................................................11 11. Pileus 10‒15 mm broad, spores ellipsoid, pseudocystidia non-septate with strongly dextrinoid contents..................... R. oss-emeri ‒ Pileus 20‒30 mm broad, spores amygdaliform, rare uniseptate pseudocystidia present, pseudocystidia with only weakly dextrinoid contents.............................................................................................................................................................................. R. brunnea

Published as part of Vizzini, Alfredo, Picillo, Bernardo, Ercole, Enrico, Vila, Jordi & Contu, Marco, 2016, Rhodocybe formosa (Agaricales, Entolomataceae): new collections, molecular data and synonymy, and Rhodocybe griseonigrella comb. nov., pp. 34-46 in Phytotaxa 255 (1) on pages 43-44, DOI: 10.11646/phytotaxa.255.1.3, http://zenodo.org/record/13675306