NEW ZEALAND: South Island: Nelson, Lake Rotoiti, track to St. Arnaud Range, under N. fusca-menziesii-solandri var. cliffortioides 30.IV.1968, leg. HORAK, PDD 27179, holotype (ZT 68/322, isotype). - Canterbury, Craigieburn Range, Broken River, near FRES Camp, under N. solandri var. cliffortioides, 19.VI.1968, leg. HORAK (ZT 68/273).

Pileus - 40 mm, convex to broadly umbonate or obtusely campanulate; fuliginous or olive-brown at centre, towards margin turning olive-yellow or bright yellow; subgelatinous to viscid, striate margin when moist, hygrophanous, conspicuous veil remnants absent. - Lamellae l0-26, -7, emarginate, subdecurrent with tooth, -6 mm wide; dark yellow (with greenish tinge) turning yellow-rust brown; edges concolorous, entire. - Stipe-70 x -4 (-13 at base) mm, slender, fusoid to subbulbous towards base, rarely cylindrical, single; yellow to olive-yellow, occasionally with yellow rhizoids; glutinous from base to evanescent cortina, longitudinally fibrillose in dry conditions, solid becoming hollow. - Context olive-brown in pileus and stipe, yellow beneath stipe's cuticle. - Odour and taste raphanoid (or like raw potatoes). - Chemical reactions  on pileus and stipe: KOH - red to red-brown; HCl, NH3 negative. Spore print rust brown. - Spores 7.5-9 x 4.5-5 µm, elliptical, minutely verrucose, with coarse warts at apex, rarely with distinct perispore, rust-brown. -Basidia 25-35 x 6-8 µm, 4-spored. - Cheilocystidia none. - Pileipellis an ixocutis composed of cylindrical, gelatinized, entangled hyphae (2-6  µm diam.), subcutis cellular, with red-brown encrusting and plasmatic pigment, readily dissolving in KOH (solvent stains red-purple). - Clamp connections present.

On soil in Nothofagus-forests. - New Zealand.

Pileus -40 mm, ex convexo obtuse campanulatus, olivaceofuligineus ad apicem, luteus marginem versus, glutinosus. Lamellae emarginatae, aureae. Stipes -70 x -4 (-13) mm, fusoideus vel subclavatus, luteus (olivaceo tinctu), glutinosus. Odor saporque raphanoidei. KOH - rubrobrunneus. Sporae 7.5-9 x 4.4-5 µm, ellipticae, minute verrucosae. Cystidia nulla. Ad terram in silvis nothofagineis. Novazelandia.

D. olivaceonigra closely resembles the more common D. alienata by similar habit, the presence of olive-green pigments (in both taxa KOH-spot test red!), the glutinous to viscid pileus and the occurrence in Nothofagus-forests. The two species, however, are distinguished by the size of the spores (larger in D. olivaceonigra) and the number and variety of anthraquinonoid pigments (KELLER & al., 1988). In D. olivaceonigra the olive-yellow colour of the carpophores is partly caused by endocrocin which lacks in the pigment chart of D. alienata.

Holotypus PDD 27179.