Rhizomes thick, woody. Culms lateral, 20-70 cm tall, 2-4 mm thick, with several cataphylls toward base. Leaves basal, ± distichous; leaf sheath dark green, open, folded, overlapping each other, 7-12 cm, leathery; leaf blade ca. 1.2 m × 2-3.5 cm or longer, subleathery, margin and abaxial midvein serrulate, apically gradually narrowed into an acutely triquetrous and flagelliform apex. Involucral bracts yellowish green, glumelike, ovate-lanceolate, 1.5-2.5 cm, slightly shorter to nearly as long as inflorescence, leathery, midvein abaxially elevated, margin brown and thickly membranous. Inflorescence a single terminal spike, ellipsoid to subobovoid, 3-3.5 × 1.5-2 cm, with many glumelike bracts and pseudospikelets. Glumelike bracts yellowish, spirally and imbricately arranged, ovate-oblong, 1.2-1.5 cm, papery. Pseudospikelets with 6 glumes, 3 male flowers, and 1 female flower; basal 2 glumes opposite, cymbiform, membranous, keeled, spinulose on apical part of keel, each subtending 1 male flower; remaining 4 bracts narrowly oblong, outermost one subtending a male flower. Filaments to 1.5 cm; anthers linear, ca. 8 mm. Style ca. 9 mm; stigmas 3. Nutlet brown, shortly stipitate, subobovoid to ellipsoid, ca. 7.5 mm, obtusely 3-sided, outer surface succulent, apex conically rostrate. Fl. and fr. Oct-Nov.
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Leaves coriaceous, linear, with only the midnerve prominent beneath and sometimes 2 of the lateral nerves somewhat prominent above, densely serrulate-scabrous throughout the margins and on the upper part of the midnerve on the lower surface, dark green, slightly narrowed towards the conduplicate base, very gradually narrowed into a long, aculeate-scabrous, triquetrous acumen, shining above, dull beneath, up to 150 by 1-2 cm; sheaths stramineous to light brown. Scapes lateral, from the caudex below the leaves, obtusely trigonous to terete, smooth, striate, very variable in length, usually much longer than in M. squamata, (2-)10-40 cm by 2-3 mm, hardly incrassate at the top, the base clothed with some ovate to oblong, striate scales up to 4 cm long. Inflorescence always a single spikelet, ovoid-conical, terete, acute, 2-4 by 1½-2 cm. Sterile glumes numerous (up to 50), the lower ones coriaceous, broadly ovate or ovate, obtuse, the upper ones oblong, chartaceous; fertile glumes 15-20 mm long, less nerved. Flowers about as long as the glumes. Anthers linear, c. 8 mm. Style 3-cleft. Keel of the outermost scales ciliate in the upper half or narrowly winged and ciliate. Nut (immature) ellipsoid or obovoid, shortly beaked, greyish brown to blackish, c. 5 by 3 mm; stipe 1 mm.
In primary forests, marshy coastal forests, along streams, at low altitudes (up to 500 m).