Shell up to 31.0 mm in length, inflated and rotund, teleoconch of 5-6 convex whorls, protoconch of 3-34 smooth, embryonic whorls, last whorl finely carinate, sutures broad and flat or narrow and canaliculate; sculptured with regular granules which are arranged in 15-33 axial ribs on the body whorl and 17-30 ribs on the penultimate whorl; the granules form 4-5 spiral rows on the penultimate and 8-10 rows on the body whorl. Columellar callus spreading onto body whorl, thinning next to parietal wall, wrinkled and laminated anteriorly; columellar denticles irregular, numbering from 5-10 and generally appearing as small plicae or wrinkles. Aperture wide and striate within, outer lip denticulate and occasionally with short spines on the edge, siphonal notch very deep, anal canal prominent. Uniformly straw-yellow, fawn or light brown in colour, body whorl occasionally with 2 broad brown bands, columellar callus white or cream, interior of aperture white, banded with purplish-grey. Periostracum thin, translucent, straw-yellow in colour. Operculum brown and serrate on margins.
N.conoidalis is a variable species as far as sculpture is concerned. The typical form conoidalis (= variegata A.Adams = cumingii A.Adams), has a sculpture of numerous, close-set, slender axial riblets. The verrucosus form (= labordei Mari) has a coarser sculpture and fewer axial ribs, while ringens and comtessei are intermediate between the conoidalis and verrucosa forms. The species is usually known under the homonymous names of clathrata Lamarck and gemmulata Lamarck, and conoidalis Deshayes in Bélanger, is the earliest replacement name available.

TYPE LOCALITY. Seas of Sondé [= Sunda Seas, Indonesia] (conoidalis); none (clathratum Lamarck; gemmulatum; ringens); Dalmaguete, Negros I, Philippines (variegata); Eastern Seas (verrucosa); China (cumingii); Rajah [= Bajah], Mantjeuri River, Bantam, Pliocene of Java (rajaensis); Sydney Har- bour, Australia (comtessei); Aden (labordei).
DISTRIBUTION. From the Red Sea and the Persian Gulf throughout the tropical Indo-Pacific to the Line Islands and questionably the Tuamotu Archipelago (record in AMS). In coralline and black sand, usually subtidal to a depth of 120 m. Type specimens. Three syntypes of N.conoidalis (Deshayes in Bélanger) are in the École des Mines, Paris, and the specimen measuring length 19.1 mm, width 12.5 mm, is here selected as the lectotype (Pl.7,fig.3). Two syntypes of Nassa variegata A.Adams, are in the British Museum (N.H.), London, and the syntype length 17.3 mm, is here selected as the lectotype (Pl.7.fig.4). The holotype of N. ver- rucosa A.Adams, is in the same Institution No. 1973120, length 23.4 mm. The holotype of N.cum- ingii A.Adams, is also in the British Museum (N.H.), No. 1962914, length 25.3 mm, as is the juvenile holotype of N.ringens Reeve (also type of Desmoulea ringens A.Adams) No. 1973166, length 15.3 mm. The type of N.rajaensis K.Martin, is in the Rijksmuseum van Geologie en Mineralogie, Leiden, the holotype of N.comtessei (Iredale), is in the Australian Museum, Sydney, No.C-57847, length 30.4 mm, and the holotype of N.labordei Mari, is in the Institut Royal des Sciences Naturelles, Brussels, length 30.0 mm.