Derivation
From Greek erion (wool) and achne (chaff or scale), possibly referring to the florets being hairy or else to the indumentum of the whole plant.

benthamii- in honour of George Bentham (1800–1884). English botanist.

Published in
J. Linn. Soc., Bot. 52: 344 (1942).

Habit
Perennial, densely tufted. Basal leaf sheaths pubescent. Culms erect or geniculately ascending, 45–90 cm tall. Mid-culm internodes pruinose. Mid-culm nodes glabrous or pubescent. Lateral branches simple or sparsely branched or branched. Leaf-sheaths tight. Ligule a fringe of hairs, 0.5–1 mm long. Leaf-blades flat or convolute, 9–18 cm long, 2–4.5 mm wide. Leaf-blade surface smooth, glabrous. Leaf-blade margins cartilaginous.

Inflorescence
Inflorescence compound, a panicle, terminal. Panicle open or contracted, oblong, dense or loose, 2.5–17 cm long, 1–3 cm wide. Primary panicle branches 3–7 cm long.

Spikelets
Spikelets solitary. Pedicels 0.5–3 mm long. Fertile spikelets 2-flowered, comprising 2 fertile florets, without rhachilla extension, ovate, laterally compressed, compressed slightly, 6–10 mm long, breaking up at maturity. Spikelets disarticulating below each fertile floret.

Glumes
Glumes opposite, persistent, similar, thinner than fertile lemma. Lower glume lanceolate to oblong, 3.5–9 mm long, equalling upper glume, membranous or cartilaginous, much thinner on margins, 9–11-nerved. Lower glume surface smooth or asperulous or scabrous, glabrous. Lower glume apex obtuse or acute or acuminate or cuspidate, muticous. Upper glume lanceolate to oblong, 3.5–9 mm long, 60–90% of length of adjacent fertile lemma, membranous or cartilaginous, with scarious margins, 9–11-nerved. Upper glume surface smooth or asperulous or scabrous, glabrous. Upper glume apex obtuse or acute or acuminate or cuspidate, muticous.

Florets
Fertile lemma elliptic or oblong, laterally compressed, 6–10 mm long, membranous or cartilaginous or coriaceous, much thinner on margins, 5–7-nerved. Lemma surface scaberulous, rough above, without grooves or with 2 longitudinal grooves, pilose. Lemma margins involute. Lemma apex acuminate, mucronate or 1-awned. Median (principal) awn 0–1.8 mm long overall. Palea gaping, coriaceous, 2-nerved. Palea surface scaberulous. Palea apex entire or dentate, 2-fid, muticous. Anthers 3, 3.8–4 mm long. Grain with adherent pericarp, obovoid, 1.5–3 mm long, dark brown, truncate. Embryo 50% of length of grain.

Continental Distribution:
Australasia.

Australian Distribution:
Western Australia, Northern Territory, South Australia, Queensland.

Western Australia: Fitzgerald, Dampier, Fortescue, Ashburton, Carnarvon, Austin. Northern Territory: Victoria River, Barkly Tableland, Central Australia North, Central Australia South. South Australia: Lake Eyre. Queensland: Cook, Burke, South Kennedy, Gregory North, Gregory South, Mitchell, Maranoa.

Classification. (GPWG 2001):
Incertae Sedis: Eriachneae

Notes
Endemic. Between 16ºS and 28ºS in S.A., Qld, N.T. and W.A. A common, often dominant, component of grassland plains, gibber plains and clay pans, in grey, brown or black, cracking clays and other heavy-textured soils. Favourable sites are usually low-lying, water-logged or seasonally flooded. Flowers and fruits Dec.–Sept. (summer to early spring).