Benthamia nigrovaginata H.Perrier, Bull. Soc. Bot. France 81: 32 (1934).
Plants terrestrial, 80 cm to 1 m. tall stem sheathed basally by 2 long (8-12 cm) sheaths without a developed limbus and of an intense black, bearing 4 distant leaves above, with the 2 inferior much larger and equally blackish as the sheaths, then above the 4 leaves, 2-3 more sheaths with a narrow-acute limbus. Leaves large, oblong-lanceolate (10-19 x 2-3 cm) and acute. Inflorescence very long (35-40 cm), many flowered, very loose, bracts narrow, acute, 1 veined, the inferiors longer than the flowers, the superiors slightly longer than the pedicel; flowers small, greenish. Sepals lanceolate-obtuse 3 5 mm long, dorsal edge slightly projecting. Petals longer than the sepals (4.5 x 1.2 mm), 2 veined basally, thickened apically labellum (5 x 1.2 mm) 3 veined, very concave, trilobed apically, lobes thick, lateral lobes a third as long as the median; spur very short (0.7mm ), saccate, compressed Anther apiculate-acute staminodes suborbicular, half as long as the anther. Rostellum short, lateral lobes small, median slightly larger and acute. Pedicel 4.5-5 mm long.
Growing on the edges of rivers, in forests, flowering, October.