North Island: WKR, at base of Big Kauri Tree, 23.vi.81, coll. RHP & Ann Hawthorne, no. 42264 (holotype, PDD; isotype, TENN); WKR, across river from Forestry Headquarters, 23.vi.81, coll. GS, no. 42419 (TENN).

Fruit bodies up to 12 x 0.5 cm, simple clubs, scattered, gregarious or cespitose in groups of up to 30 individuals, narrowly fusiform to subcylindrical, arising from discrete or common whitish mycelial patches. Club slate-grey to deep slate-grey ("Quaker-drab", "deep purplish grey", "purplish grey", "neutral grey", "deep neutral grey"), opaque, with mat texture, often longitudinally wrinkled or dimpled, equal; flesh concolourous outward, inward whitish and stuffed; apex rounded. Stipe equal, hardly distinct from hymenium, deep grey-brown ("benzo-brown" upward, "drab" downward). Taste faintly sweet; odour none, or tardily and weakly of garlic.
Macrochemical reaction: FCL = negative.
Tramal hyphae significantly inflated, adherent, thin-walled, clampless, hyaline; secondary septa rare; gloeoplerous hyphae occasional, uninflated, refringent under phase contrast. Subhymenium well-developed, pseudoparenchymatous. Hymenium thickening, adherent; basidia (Figs 18, 19) clavate, clamped, contents granular when young, multiguttulate when mature; sterigmata 4, stout, curved, somewhat divergent.
Spores 8.3-11.2 x 6.8-8.3 µm (E = 1.19-1.50; E^m = 1.32; L^m = 9.83 µm), broadly ellipsoid, flattened slightly adaxially, smooth, thin-walled; contents uniguttulate when mature; hilar appendix thick, prominent, papillate.

On soil and humus under kauri (Agathis australis).

Receptacula ad 120 x 5 mm, simplicia, gregaria vel caespitosa, ardosiaca ad murina. Hyphis efibulatis; basidiis fibulatis. Sporis ut in oratione infra.

This is a slate-grey version of Clavaria albo-globospora, with which it was growing. Fruit bodies are striking when once seen but the dark colour obscures them in the field.
Clavaria muscula from Australia is very similar in fruit body colour, but does not produce cespitose clusters of clubs, and forms smaller spores (6.7-8.1 x 5.2-6.3 µm; L^m = 7.51 µm) than C. ardosiaca. These species seem to stand in much the same relative position as C. alliacea (q.v.) and C. albo-globospora.

North Island: WKR, Te Matua Ngahere, base of big tree, 31.v.82, coll. RHP, no. 43541 (holotype, PDD; isotype, TENN); Auckland, Orere, 4.vii.81, coll. EH, no. 1042 (ZT); OSF, 5.v.81, coll. EH, no. 604 (ZT); WR, Cowan Track, 4.vi.83, coll. GS & A Rossman, s.n. (PDD); Auckland, Titirangi, Atkinson Park, 20.vi.65, coll. RFRM, no. 64 (PDD). South Island: PSR,19.v.83, no. 43540 (TENN).

Fruit bodies up to 60 x 4 mm, simple clubs, solitary to cespitose in groups of 2-3, arising from a small, whitish mycelial patch. Stipe equal, pallid at base ("tileul buff") grey above ("pale neutral-grey"), appearing silky. Club matte on surface, equal, often somewhat wrinkled or subsulcate, grey to bluish grey ["neutral-grey", "7 grey" "deep dull grey", "deep plumbeus", "mouse-grey"]; flesh more deeply coloured than hymenium outward, paler and more fibrous or stuffed within. Apex rounded. Taste and odour negligible.
Macrochemical reaction: FCL = negative.
Tramal hyphae of club 3-20 µm diam., hyaline, unclamped, thin-walled, strictly parallel, covered with small patches of amorphous material, and with occasional crystals. Subhymenium extensive, pseudoparenchymatous. Hymenium thickening; basidia 70-80 x 10-13 µm, broadly clavate, bifurcate or clamped at base, more or less persistent after spore discharge; contents granular to multiguttulate at maturity; sterigmata (2-3)-4, stout, arising as rounded lobes, eventually up to 10 µm long, curved-ascending.
Spores (Fig. 28) 9.4-11.2 x 7.9-9.0 µm (E = 1.08-1.41; E^m = 1.21; L^m = 10.3 µm), broadly ellipsoid, conspicuously roughened; contents multiguttulate to uniguttulate; hilar appendix broad, papillate; ornamentation of narrowly truncate-conical spines up to 1.5 µm long.

Receptacula ad 60 x 4 mm, simplicia, solitaria vel gregaria, caesia, murina. Hyphis efibulatis; basidiis fibulatis. Sporis ellipsoideis, echinulatis, ut in oratione infra.

Again, spore ornamentation provides a most confusing situation. Clavaria ardosiaca not only shares almost identical fruit bodies (colour, stature, etc.) but unusually large spores, however, its spores are smooth. At the same time, C. musculo-spinosa specimens vary greatly in this character, for TENN no. 43541 and Horak's collections show almost no smooth spores, whereas TENN no. 43540 shows very few ornamented spores. Were the rough spores not seen on TENN no. 43541, it would surely have been accessioned under C. ardosiaca. Thus, although it would appear that species pairs exist - one with ornamented spores, the other with smooth-this maybe artifactual, really representing a cline under unknown controls.
The wide, long basidia are a reflection of the large spores. Sterigmata number is very variable, perhaps (as in many other taxa) related to the unusual variation in spore dimensions and E values. Sterigmata are blunt until near maturity.