Diagnosis . Bulbophyllum hamatum resembles B. omerandrum in free lateral sepals, petals bearing fimbriate-ciliate margin, and fleshy recurved ligulate lip, but differs in hooked or falcate stelidia, caudate dorsal sepal and petals, and ovoid column wings.
Description . Epiphytic or lithophytic herb. Rhizome creeping, quantity2 mm in diam., rooting from base of pseudobulbs. Pseudobulbs quantity1–7 cm apart on rhizome, narrowly pyriform to subcylindric, quantity1–2.5 cm , quantity0.3–1.2 cm in diam., with a terminal leaf. Petiole quantity1–2 cm ; leaf oblong, 3–8.5 × quantity0.7–1.6 cm , thick, leathery, base cuneate, apex obtuse and retuse, mid-vine concave adaxialy, convex abaxialy. Scape arising from base of pseudobulb, erect, usually quantity5–9 cm ; condensed raceme 2–4-flowered; peduncle slender, ca. quantity1 mm in diam., 2 or 3 tubular sheaths, placed sparsely; floral bracts ovate, cymbiform, quantity8–12 mm . Pedicel and ovary quantity1.2–2 cm , densely purple spotted. Flowers yellowish white. Dorsal sepal broadly ovate, 6–10 × quantity5 mm , apex long acuminate to caudate, margin entire, 4–5-veined; lateral sepals usually free, narrowly falcate-lanceolate, 16–22 × quantity5 mm , base adnate to column foot, margin entire, twisted near base and divergent, apex acuminate. Petals ovate or ovate-triangular, 5 × quantity4 mm , tip caudate with a thread quantity2–3 mm , margins finely erose to deeply lacerate distally, 3-veined; lip recurved, ligulate, ca. quantity6 mm , fleshy, base attached to end of column foot by a mobile joint, apex obtuse and apiculate, sparsely finely papillate on both sides. Column ca. quantity5 mm , with ovoid wings at upper part; foot curved, ca. quantity4mm , with free part ca. quantity3 mm ; stelidia hooked or falcate, ca. quantity2 mm ; anther cap comblike on apical margin; pollinia 4, in 2 pairs.
Etymology . The specific epithet “ hamatum ” refers to the hooked or falcate stelidia in this new species.
Phenology . Flowering in April to May, fruiting in May.
Distribution and habitat . B. hamatum grows in Wufeng County, collectingRegionHubei , collectingCountryChina , on damp moss rocks and trees in the subtropical evergreen broad-leaved forest at the elevation quantity950–1200 m . Three subpopulations were found around the typeStatustype locality.
Taxonomic note : B. hamatum mainly differs from B. omerandrum in hooked or falcate stelidia. The morphological differences between them were summarized in Table 1 and Fig. 2 .