Small agaric, growing on litter, rarely on wood, with a white spore print. Pileus white or pale, with a blue-green bloom, not viscid. Lamellae widely spaced and with interconnections. Stipe off-centre or lateral. No partial veil remnants. Spores triangular, with a few large projecting nodules, hyaline, non-amyloid, smooth; germ pore absent. Cheilocystidia present. Lamellar trama regular. Pileipellis a cutis or a trichoderm, composed of nodulose hyphae. Clamp connections present.

The other species of Tetrapyrgos (T. nigripes) has a central stipe. Campanella is similar, but lacks the nodulose spores.

One species: Tetrapyrgos olivaceonigra (= Pterospora, Campanella).

Tetrapyrgos nigripes, with a central stipe, is keyed out separately.

Tetrapyrgos olivaceonigra (E.Horak) E.Horak, Sydowia 39: 102 (1987).

Vic. and Tas. (and probably also Qld and N.S.W.).

In native forests.

On litter or wood.

Saprotrophic.

Fuhrer, B. (2005), A Field Guide to Australian Fungi. Bloomings Books, Hawthorn. [Description and Illustration of T. olivaceonigra (as Campanella)]

Horak, E. (1983b), Neufunde und Bemerkungen zu einem emendierten Gattungskonzept von Pterospora Métrod (Agaricales), Sydowia 36: 125–138. [Description, B&W Illustration and Microcharacters of T. olivaceonigra (as Peterospora)]

May, T. (1989), Report of F.N.C.V. fungal excursions: 1986–1988, Vict. Naturalist 106: 48–58. [Description, B&W Illustration and Microcharacters of T. olivaceonigra]

McCann, I.R. (2003), Australian Fungi Illustrated. Macdown Productions, Vermont. [Illustration of T. olivaceonigra (as Campanella)]