Slender, flat-leaved, extravaginally branching, stoloniferous, tuft-forming perennial grass with rough patent spikelets on a short inflorescence. Leafsheath 2.5-5 cm, glabrous or retrorsely short hairy, thin, becoming fibrous below, sometimes reddened, margin hyaline. Auricles 0.1-0.5 mm, glabrous, barely clasping. Ligule 0.6-1.25 mm, lacerate. Collar dark brown or purpled, glabrous. Leaf-blade 6-25 cm × 0.5-3.5 mm, soft, flat, thin, adaxially veins hirsute or minutely scabrid; margins glabrous below, prickle teeth above; abaxially with conspicuous white midrib and 2 white lateral veins, evident prickle teeth on nerves above. Culm 17- 60 cm, slender, geniculate and decumbent below; nodes conspicuous, swollen, usually 3, dark brown or almost black; internodes glabrous or antrorsely lanate immediately below inflorescence. Inflorescence a spike-like raceme 3-13 cm, subtended by a small hair-fringed bract; spikelets 4-13, imbricate; rachis internodes short, sulcate, antrorsely toothed on margins, elsewhere antrorsely lanate or glabrous. Spikelets 10-14 mm, of 4-6 florets on short (0.3 mm) hairy pedicels, broadside to tough rachis, becoming patent. Glumes unequal, narrowly or broadly triangular-acute, < spikelet, with 3-5 evident white veins, keels excentric, abaxially irregularly prickle-toothed, adaxially clothed in short white stiff antrorse hairs, margin very narrowly chartaceous, toothed; lower 2.5-4 mm, upper 3.7-5.5 mm. Lemma 9-11 mm including indefinite canaliculate "awn" 1.5-4 mm, 5-nerved, keel obscure below, abaxially with abundant antrorse, ± appressed prickle teeth, margin very narrowly chartaceous, toothed. Palea 5.3-7 mm; keels shortly denticulate; apex shallowly bifid, ciliate; abaxial interkeels with abundant short, white, stiff, antrorse hairs; flanks with short hairs at apex and along margin. Callus 0.25-0.4 mm, surrounded adaxially by short stiff hairs; disarticulation oblique. Rachilla 1.0-1.25 mm, with stiff appressed white hairs. Lodicules 0.4- 0.6 mm, ciliate. Anthers 2.4-2.75 mm. Gynoecium: ovary 0.8-1 mm, hispid hairs at apex; stigma-styles 1.75-2 mm. Caryopsis 3.5-4 mm, linear, adherent to palea; hilum linear, 3.5-3.75 mm, embryo 0.75 mm.

Gramen tenue, stolones emittens, laxe extravaginaliter ramificans; vagina glabra vel pilis brevibus retrorsis ornata; auriculae parvae, glabrae; ligula lacerata. Lamina plana, tenuis, hirsuta vel adaxialiter hispida. Culmus nodis tumidis geniculatis atrobrunneis internodiisque glabris praeditus. Inflorescentia brevis, spiculas numerosas in pedicellis brevibus, demum patentes, gerens. Glumae foliaceae, hebetes, dentibus minimis rigidis abaxialiter instructae. Lemma dentibus minimis rigidis abundantibus indutum usque ad apicis aristiformis extremitatem. Antherae ad 2.7 mm. Chromosomata In = 14, diploidea. A. pectinato (Labill.) A. Love accedit, a quo tamen praecipue differt dentibus minimis rigidis usque ad lemmatis glumarumque apices, et inflorescentiae internodiis longioribus.

Ab A. calcis ssp. calcis pilis super nervis in adaxiali laminae pagina, et dentibus longioribus rigidis in abaxiali lemmatis pagina diagnoscenda.