From the Greek, arachnion, spider's web + odes, perhaps in allusion to a fancied resemblance of one of the more finely dissected pentagonal species, to a spider's web.
Rhizome: long creeping, tan scales lanceolate.
Frond: evergreen, monomorphic.
Stipe: lanceolate scales, vascular bundles: 4 or more in an arc.
Blade: 2-pinnate-pinnatifid to 3-pinnate or more, deltate or pentagonal, papery to somewhat leathery, below: hairlike scales.
Pinnae: anadromous, proximal pinnae largest, with basal basiscopic pinnule much larger, costae shallowly grooved above, continuous from rachis to costae, segments margins spiny, ultimate segments frequently mucronate, veins free, forked.
Sori: round, between midrib and margin, indusium: reniform, attached at a sinus, sporangia: translucent.
Arachniodes shares the kidney-shaped indusia and grooves continuous from rachis to costae with Dryopteris (disputed in the Flora of Australia); it differs in an anadromic plan throughout whereas Dryopteris is catadromic above the basal pinna pair, and is said to have creeping rhizomes rather than erect ones, an unconvincing distinction, given a number of species with short-creeping rhizomes in Dryopteris. A mucronate, or bristle-like, terminus at the ends of veins is also present in Arachnoides, a feature shared with many Polystichum.