Full name: Hebeloma argentinum Speg. (1898)
Published: Anales del Museo Nacional de Historia Natural Buenos Aires 6: 129 (1898)
Taxonomic status: We have not been able to unambiguously determine the current genus of this name.
Original diagnosis: Diag. Denudatum pusillam subsolitarium, pileo convexulo umbonatulo roseo-testaceo laevi glabro non striato, lamellis sinuato-adnatis pallide ochraceis, stipite fibroso torto candido laevi v. squarruloso, stricte cavo, sporis ovatis laevibus. Hab. Ad terram nudan in dumetis, Parque de La Plata. Apr. 1892. Obs. Solitarium v. subcaespitosum; pileus carnosulus primo globosus v. ovatus dein gradatim expansus, postremo hemisphaerico-applanatus (15-30 mm diam.) centro plus minusve grosse obtuseque umbonatus, glaber laevis (in sicco) sub lente valida subpulverulentus subnitens v. vernicosus pulchre pallideque e roseo v. violaceo cinerascens v. lateritius, ambitu non v. vix pallidior, margine decoloratus acutus integer exappendiculatus; caro centro subcrassiuscula (2-3 mm crass.) compactiuscula alba; lamellae confertiusculae polvmacriae membra-naceo-carnosulae latiusculae (3-4 mm lat.) antice acutato-rotundatae postice sinuato-subadnatae non v. vix denticulo subdecurrentes pallide ochroleucae v. ochraceae acie integrae; stipes erectus, rectus v. flexuosulus teres (25-50 mm long. = 2-5 mm diam.) fibroso-carnosulus saepius tortus candidius v. subpallescens, glaber laevis, vix in parte supera (rarius medio v. basi) laxe minuteque fibrilloso-squamulosus, basi non v. vix inerassatus, mycelio albo-gossypino parcissimo ornatus, intus e farcto cavus atque fusco-albescens; basidia clavulata (25 μ long. = 10 μ diam.) hyalina; sporae ovatae v. subpyriformes (10-16 μ (saepius 12-14) long.= 7-8 μ diam.) e roseo ochraceae. Species pulcherrima odore et sapore fere nullis.

English translation: Diag. Bare small almost solitary, pileus slightly convex subumbonate pinkish-brick red smooth glabrous non-striate, lamellae sinuate-adnate pale ochraceous, stipe fibrous twisted pure white smooth or slightly squarrose, narrowly hollow, spores ovoid smooth. Hab. On bare ground in thickets, Park of La Plata, Apr. 1892. Obs. Solitary or subcaespitose; pileus slightly fleshy at first globose or ovate then gradually expanded, finally hemispherical to applanate (15-30 mm in diameter) in the centre more or less coarsely and obtusely umbonate, glabrous, smooth (when dry) under a good magnifying-glass subpulverulent slightly shiny or varnished beautifully and palely pinkish or violaceous-grey or brick red, on the marginal area not or just paler, margin colourless acute entire non-appendiculate; context slightly fleshy in the centre (2-3 mm thick) rather firm white; lamellae subcrowded, of various length membranous to rather fleshy moderaly broad (3-4 mm broad) externally acute-rounded, at the back sinuate-subadnate not or subdecurrent with a tooth very pale ochraceous or ochraceous with entire edge; stipe upright, straight or slightly flexuous terete (25-50 mm long. = 2-5 mm thick), fibrous slightly fleshy twisted pure white or becoming somewhat pale, glabrous smooth just loosely fibrillose-squamulose on the upper part (rarely in the middle or at the base), at base not or just enlarged, with very scanty white cottony mycelium, on the inside stuffed to hollow and pale brown; basidia small clavate (25 μ long. = 10 μ wide) hyaline; spores ovoid or subpyriform (10-16 μ (often 12-14) long.= 7.8 μ wide) pink to ochraceous. A very beautiful species with smell and taste almost absent.

Commentary: Within the latin diagnosis, *”Denudatum” (denuded, bare, stripped of covering) is ambiguous. It may refer to the lack of veil (Fries’ Denudati) or it may simply be a synonym of glabrous, lachink scales etc. The term "polymacriae" is a Greek compound, rarely used and taken to mean “of many dimensions”; referring to lamellae it probably should be interpreted as “of various length”. Thus far we have been unable to study type material of this taxon. Based on the diagnosis, it is not possible to determine whether this is a Hebeloma.