The species is characterised by numerous large and most prominently ornamented cystidia with regular ornamentation and by moderately broad fusiform basidiospores 10.5–12.5 × 2.5–3.5 µm.

JAMAICA. Cornwall County: Trelawny parish, Windsor Cave, along trail to Troy, 18.3564, -77.6472, on trunk of angiosperm tree, 13 Jun 1999, K.-H.Larsson (KHL 10813 in GB).

robustius (Lat.), having large cystidia with large crystal protrusions.

Basidiomata annual, effused, resupinate, soft and fragile, arachnoid, loosely adnate and easily separable. Hymenophore smooth, hirsute due to numerous protruding large cystidia, yellowish. Margin thinning out, pruinose, adnate.

system monomitic. All septa with clamps. Subiculum thick, with interwoven richly branched hyphae 2–3 µm wide, thin-walled to slightly thick-walled, hyaline to yellowish, smooth or with sparse granulose encrustation. Subhymenium rather thick, up to 60 µm. Subhymenial hyphae richly branched, intricate, regular or occasionally slightly inflated, 2–4 µm wide, thin-walled, occasionally weakly encrusted by yellowish crystalline material. Cystidia subulate, 80–105 × 4.5–6 µm including encrustation, projecting up to 65 µm, without basal swelling, terminal or pleural, with thick yellowish wall and outer hyaline crystalline sheath covering the whole cystidium except the small tapering or acuminate apex. Crystal protrusions on cystidium are large and clearly rectangular, arranged in longitudinal rows.

Basidia clavate to suburniform, 13–20 × 4–6 µm, thin-walled, with 4 sterigmata and a basal clamp, without encrustation or rarely with a slight crystalline crust at the base. Basidiospores fusiform, adaxial side convex, L= (8.1–)8.5–10.9(–11.7) µm, W=(2.5–)2.7–3.5(–3.7) µm, Q=(2.4–)2.6–3.6(–4.0), N=197/4, with minute apiculus, smooth, thin-walled, hyaline, negative in Melzer’s reagent. Tolerance limits for basidiospore length, width and length to width ratio in S. robustius, based on 4 sequenced specimens, are provided in Table 2.

BRAZIL. Sao Paulo: Cananeia, Ilha do Cardoso, -25.1336, -47.9617, on dead wood, 2-5 Feb 1987, D.Pegler, K.Hjortstam & L.Ryvarden (LR 24792 in O:F). COLOMBIA. Magdalena: Parque Nacional Tayrona, Estacion de Gairaca, 0-30 m, 11.3170, -74.1063, on dead wood, 12 Jun 1978, L.Ryvarden (LR 15791 in O:F 918494). COSTA RICA. Alajuela: Bijagua, Albergue Heliconias, Sendero Heliconias, 770 m, 10.7181, -85.0453, on log of angiosperm tree, 12 Jul 2001, K.-H.Larsson (KHL 11245 and 11259 in GB); San Ramon, Reserva Forestal Colonia Palmarena, 850 m., 10.2500, -84.5667, on dead wood, 14 Mar 1991, L.Horovitz (FO 42968 in TUB). ECUADOR. Orellana: Yasuni National Park, Yasuni Scientific Research Station, -0.6859, -76.3953, on dead wood, 9-12 Mar 2002, L.Ryvarden (LR 44667 in O:F 505981 and LR 44688 in O:F 505799). JAMAICA. Cornwall County: Trelawny parish, N of Crowlands, trail/road into park area, 18.2611, -77.6511, on stem of angiosperm tree, 10 Jun 1999, K.-H.Larsson (KHL 10661 in GB); Windsor Cave, along trail to Troy, 18.3564, -77.6472, on trunk of angiosperm tree, 13 Jun 1999, K.-H.Larsson (KHL 10780 and 10814 in GB). Surrey County: Portland parish, between reach and Ecclesdown hillside to the east, alt 500 m, 18.0433, -76.3108, on of angiosperm trunk, 16 Jun 1999, K.-H.Larsson (KHL 10895 in GB). PUERTO RICO. Municipio Juana Diaz, Bosque Estatal Toro Negro, near DNR office, downstream from Road 143, 18.1539, -66.5356, on dead wood, 24 Jun 1996, K.-H.Larsson (KHL 9381 in GB). Municipio Luquillo, Luquillo Mts, Bisley Experimental Watersheds, along the logging road, 215 m a.s.l., 18.3161, -65.7467, on log of angiosperm tree, 6 Jun 1997, K.-H.Larsson (KHL 10039 in GB); Sabana, above Chicken Farm & Rio Sabana, 70 m a.s.l., 18.3500, -65.7344, on log, 10 Jun 1998, K.-H.Larsson (KHL 10423 in GB). Municipio Maricao, Reserva Forestal Maricao, near Fish Hatchery, 18.1922, -66.9933, on decaying log of angiosperm tree, 25 Jun 1996, K.-H.Larsson (KHL 9454 in GB). Municipio Rio Grande, Luquillo Mts, El Verde Research Area, between Field Station and 16-hectare grid, 320-380 m, 18.3233, -65.8172, on log, 7 Jun 1998, K.-H.Larsson (KHL 10272 in GB); El Verde Research Area, lower part of 16-hectare grid, 345-360 m, 18.3239, -65.8172, on dead wood, 28 Jun 1996, K.-H.Larsson (KHL 9574 in GB). VENEZUELA. Estado Amazonas: Manapiare, Yutajé, 5.6142, -66.1236, on dead wood of angiosperm tree, 12-19 Apr 1998, L.Ryvarden (LR 40545 in O:F). Estado Aragua: Maracay, National Park Henri Pittier, Rancho Grande, 10.3800, -67.6190, on dead wood of angiosperm tree, 25 Apr 1998, L.Ryvarden (LR 40767 in O:F).

Our data shows that the species is widespread in the Caribbean region and in South America. We were able to examine the specimen mentioned and illustrated from Costa Rica by Kisimova-Horovitz et al. (1997) under the name S. naviculatum and re-identified it as S. robustius.