Summary. Chaetocalyx subulatus, a new species from Bahia, Brazil, is described and illustrated. Chaetocalyx is a small New World genus of climbing papilionoid legumes. Collectively, the fourteen species recorded to date range from southern Mexico through Central and South America, westward to Peru and southward to northern Argentina, southern Brazil and Uruguay. The plant described here was first identified as a novelty by G. P. Lewis during the preparation of his book Legumes of Bahia (1987), and later confirmed by V. E. Rudd. Since the publication of Rudd's revision of the genus in 1958 this is only the third species to be described as new to science. Chaetocalyx bracteosa from eastern Brazil was published by Rudd in 1972 and C. chacoensis from Paraguay was described by Vanni in 1981. This species is recognised by a number of characters, most distinctive of which are its subulate calyx-lobes which are considerably longer than any other members of the genus. Chaetocalyx subulatus Mackinder sp. nov. C. blanchetianae (Benth.) Rudd valde affinis sed lobis calycis multo longioribus subulatis 0.7-1.8 cm et sparse pilis patentibus vivide aurantiis usque 1 mm longis instructis, lamina vexilli longiore usque 2.2 cm, et pedunculo longiore usque 10 cm distincta. Typus: Brazil, Bahia, Hatschbach 46535 (holotypus MBM; isotypus K). Twining slender herb; stems, stipules, bracts and all axes of the plant fulvous-pubescent with bristly golden glandular hairs interspersed. Stipules 5-6 x 2 mm, lanceolate, acute. Leaves imparipinnate with 5-7 leaflets, petiole 3.2-5 cm long, leaf rachis 5.8-7 cm long; leaflets elliptic, 4.4-5.2 x 2.8-3.3 cm, mucronate, glabrous on the upper surface, pubescent on the lower surface with golden glandular hairs along the mid vein and basal margin. Inflorescence axillary, 4-6-flowered; peduncle 9.2-10cm long; bracts rhomboid, 4 x 2 mm; pedicels 1.5-1.8 cm long. Calyx campanulate, gibbous, pubescent, with longer (1 mm) glandular hairs intermixed; tube 0.5-0.8 cm long; lobes subulate, 0.7-1.8 cm. Standard broadly elliptic to rotund, claw 0.5-0.6 cm, blade 2.0-2.2 cm long, pubescent on the outer surface, wings and keel-petals slightly shorter, their claws and lower margins pubescent. Stamens fused for half their length, sparsely sericeous. Ovary sessile, 10-12-ovuled, 0.9-1.2 cm long, pubescent. Fruit unknown. (Fig. 1). BRAZIL. Bahia, Municipio of Rio de Contas, Tamandua 17 May 1983, G. Hatschbach 46535 (holotype MBM; isotype K).