Description: Shell 8.2 x 3.0 mm (holotype). narrowly fusiform, truncated anteriorly; 7.5 whorls. Protoconch of 2.5 smooth glassy whorls, except the last 0.25 whorl with ~4 faint axial riblets; whorls dark brown, lighter mid-whorl. Teleoconch of 5 whorls; first whorl with 4 spiral cords, uppermost a subsutural cord slightly thicker than the second, third is swollen where it overrides the ribs and forms the periphery of the shell, fourth lies next to the suture with the succeeding whorl and is very fine. Spiral cords increase to 6 on the penultimate whorl, the 3 peripheral ones are slightly swollen across the ribs. Subsutural cord heaviest and 2 in the sulcus, which is Hat. Body whorl has a total of 15 spiral cords: 6 to the suture line as in the penultimate whorl, 4 more on shell base that are slightly swollen across the ribs, and 5 encircle the anterior canal. Distinct spiral threads are packed between (lie spiral cords, from about the third teleoconch whorl to the anterior canal. Ribs begin about midway in the sulcus and evanesce on shell base; number 11 to the varix on body whorl, 12 on penulti¬mate; distance between the ribs less than the rib width. Varix lies close to the edge of the outer lip, just behind the anal sinus, and is broader and higher than the ribs. Outer lip thin, scalloped by the ends of spiral cords, and with a slight stromboid notch. Anal sinus u-shaped, shallow, slightly constricted on parietal side by callus; located just below subsutural cord. Inner lip narrow, appressed to the columella and parietal wall, terminating posteriorly at the parietal callus that forms the roof of the aperture. Aperture ovate, about 37% of the overall height of the shell, including the anterior canal, which is very short. Shell color very dark brown to black, spiral threads between the two peripheral cords, and between subsutural cord and suture are dark brown to black; spiral cords whitish; subsutural cord brown.

This species has the characteristics of the genus Buchema, with spiral cords overriding relatively broad ribs, and spiral threads in between the cords. B. nigra is most similar to the black form of B. bellula, but its peripheral cords are less swollen on the rib crests, and it has a brown subsutural cord, which is white in B. bellula.
Unlike B. bellula, little variation is seen in specimens of B. nigra from different localities within its known range. The specimen from Man of War Bay, Tobago is indistinguishable from the holotype (Petit Nevis, SVG), as is the specimen from Grenada. An undescribed species from off Arraial do Cabo, Rio de Janeiro state, Brazil, has similar sculpture but is larger and brown in color. Only this single imperfect specimen was available, so no further analysis was undertaken.

Type Locality: Petit Nevis, St. Vincent and the Gren¬adines, in 8.5 m.
Distribution: SVG (Baliceaux I.; Petit Nevis); Grenada (Grenada I.; Carriaeou I.); and Trinidad and Tobago (Tobago I.).