B. stimpsonianum. Lectotype in MCZ No. 186378; 18.3 X 8.1 mm. Panama.

N. fuscata. Holotype in the B.M.N.H. No. 197337; 21.4 X 12.2 x 11.4 mm. Uniformly brown in colour, aperture cream-coloured, with 4 spiral rows of risen threads upon the axial ribs on the penultimate and 8 rows on the body whorl, interspaces of main spiral cords with very fine spiral striae, columella with 8 weak denticles and a parietal fold, outer lip with 7 denticles. Locality unknown.

N. lauta: 16.5 X 8.3 X 8.2 mm. Violet-brown in colour, spiral cords pale, sculptured with 7 axial ribs and 3 main spiral cords on the penultimate and 8 ribs and 9 spiral cords on the body whorl, interspaces of main spiral cords with 5-6 very fine spiral striae, columella with 6 plicae, outer lip with 5 denticles. Malacca = error.

Tomlin (1932) considered N. fuscatus to be a synonym of N. myristicatus (Hinds) but the two species are very dissimilar. The holotype of N. fuscatus is somewhat broader and has slightly more axial ribs but has the same typical sculpture of fine intermediate spiral striae as N. stimpsonianus and N. lautus. N. stimpsonianus (C. B. Adams) is a larger (16-22 mm) and more solid species than N. scabriusculus (Powys) (9-12 mm) and is usually, but not always, more conically-ovate and has wider spaced axial ribs and very fine, crowded intermediate spiral striae between the main spiral cords. The spiral cords produce interrupted, paler and heavier threads upon the axial ribs, but are weak or obsolete in between the ribs.