Description from Flora of China
Calcearia Blume; Corysanthes R. Brown; Nematoceras J. D. Hooker.
Herbs, terrestrial or rarely epiphytic, small. Tuber solitary, globose to ovoid; subterranean stem and roots slender, fleshy, pubescent. Stem slender, erect, sometimes short and remaining subterranean, usually angled or winged, with a membranous tubular cataphyll at base. Leaf solitary (rarely 2), cordate or broadly ovate, entire or rarely 3- or 5-lobed, sessile or with a short petiole-like base, often appressed to ground, with 1-3 main veins, venation usually white or red. Floral bracts 1 or 2. Flower terminal, solitary, nearly sessile, resupinate, held ± erect at leaf base; ovary usually 6-ridged. Dorsal sepal hoodlike and curved over lip, basal margin incurved and forming a tube that embraces base of lip; lateral sepals and petals linear, narrow, free or connate at base; lip deeply channeled at base and forming a decurved tube with dorsal sepal, upper limb enlarged, spreading or reflexed, adaxially usually minutely papillose or hairy, with 2 spurs or auricles (rarely neither) at base. Column short; anther terminal, erect, 2-locular; pollinia 4 or 2 with cleft, granular-farinaceous, without caudicles, directly attached to sticky viscidium; rostellum dorsal; stigma entire, concave. Capsule strongly 6-ridged, borne on elongate pedicel.
About 100 species: mainly in New Guinea, Australia, and the Pacific islands, extending through SE Asia to the Himalayas; five species (four endemic) in China.
(Authors: Chen Xinqi (陈心启 Chen Sing-chi); Stephan W. Gale, Phillip J. Cribb)