Hymenophore perennial, solitary, dimidiate, hard and woody. Pileus applanate or ungulate, variable in size and shape, 3-20 cm. x 3-12 cm. x 1-10 cm.; surface at first ochraceous or fawn, even and finely tomentose, becoming bay brown banded with greyish zones, tobacco- or fuscous-brown and concolorous, umber or in old specimens sometimes black, strongly concentrically sulcate, often banded with zones of different shades of grey or brown, more numerous and narrower peripherally, cuticle to 1 mm. thick, firm, ligneous, brittle, chestnut brown with an orange zone in the context immediately beneath, composed of hyphae with chestnut brown walls, densely woven and firmly cemented in mucilage; margin bluntly rounded, or thickened and formed from numerous equal layers, then laterally sulcate; hymenial surface at first white or cream, even, with rounded sterile margin 2-3 mm. wide, plane, slightly concave or as often convex, drying isabelline, or darker, dissepiments not toothed. Context cream or isabelline, floccose, firm, to 15 mm. thick, often zoned; skeletal hyphae 3.5-4 μ thick, lumen 2 μ or less, long type, aseptate, sparsely branched and undulate near ends, staining blue; generative hyphae 2-3 μ thick, thin walled, sparsely branched, septate only in the subhymenium, not staining. Pores in many often obscure strata, sometimes with bands of context between layers, round or slightly angular, in section wood colour, 3-10 mm. deep in each layer, 50-150 μ diameter, or 6-7 per mm.; dissepiments 50-200 μ thick, commonly 75-100 μ, equal, apices even. Basidial type clavate, basidia clavate, 8-10 x 4-5 μ, soon collapsing. Spores elliptic-oblong, or subcylindrical, 1-6 x 2-2.5 μ, smooth, hyaline.

As with many perennial species the hymenophore exhibits considerable diversity in form, size, and colour. Commonly applanate, specimens may also be ungulate, or even resupinate, though this last condition is rare. Each successive pore layer may grow to the edge of the preceding, when the margin becomes thick and banded with as many sulcate zones as there are pore layers. Or successive layers may recede, forming islands or producing irregular obconic hymenophores. Pores may be in definite strata, each defined by a differently coloured line, or by layers of context hyphae; in other specimens they may be obscurely stratose or appear to be continuous. Many stratose specimens possess a well developed ligneous cuticle; but in first year plants this is poorly developed or wanting, the surface often being finely tomentose and azonate. The basidial type is clavate, though in a former paper (1947) I erroneously stated that in both F. annosa and F. hemitephra it was of the honeycomb type. The hymenial laver (as in all species recorded herein) soon collapses after spores are shed and appears on walls of dissepiments as a formless mucilaginous film.

According to overseas workers the species resembles closely “Fomes” hormodermus Mont. Lloyd (1915, p. 215), in fact, recorded the latter from New Zealand, basing his record on specimens of F. hemitephra. The latter differs in the elliptic-oblong spores, smaller pores and presence of an orange zone in the context beneath the cuticle. Sometimes this last feature is absent, especially from young specimens; it may then be seen where the hymenophore junctions with the host. Occasionally the surface of the wood is stained orange.