Shell to 40.0 mm in length, teleoconch of 6-7 whorls, protoconch of 2-3½ obsoletely carinate embryonic whorls; sculptured with strong axial ribs which frequently become nodose at the body whorl suture; interspaces smooth in Pacific populations but with 2-3 weak or very strong spiral grooves on penultimate whorl in Western Indian Ocean populations. Apertural callus either large and promi- nent and sometimes extending to the penultimate whorl, or smaller and not quite reaching body whor suture, anal and siphonal canals prominent, aperture strongly lirate, parietal denticle prominent, base of columella with up to 6 denticles, base of shell with 4-6 close-set spiral ridges, fasciolar cord promi- nent. Cream, grey or brown in colour, sometimes with darker bands or dark brown spots between body whorl nodes, apertural callus porcellaneous-white. Operculum brown, variously serrate at margin. TYPE LOCALITY. Unknown (arcularia and scalariformis); Timor, Indonesia, is here designated as the type locality.

DISTRIBUTION. From Sri Lanka to the Cocos-Keeling Is, Ryukyu and Tonga Islands. In clean and muddy sand, intertidal to 8 m. Type specimens. An adult specimen of N. arcularia (Linnaeus), is in the Linnean Society collection, London, length 28.1 mm, width 18.1 mm; this specimen has the "Systema Naturae ed. 12" number, and it is the typical smooth form of the species. The type-specimen of scalariformis Moerch, based on a juvenile specimen, is no longer extant. Material examined. SRI LANKA: (AIM; USNM); Back Bay, Trincomalee (ZMC); ANDAMAN IS.: (ZSI); NICOBAR IS.: Galathea Bay, Gt.Nicobar I, 8 m (ZMC); INDONESIA: Sibuan I, Borneo; Domaring, Borneo; Pulau Stupai, Sumatra; Mentawai Is.; Soemoer, Bantam, Java; Tomahu I, Moluccas; Gamoms I, Celebes; Tagnak I, Borneo (all USNM); Lontor, Banda I; Doe Roa, Kei-Oerne, Kai Is (both ZMC); Daeo, S.coast of Morotai, Malaka; Pantai Kelapa Lima, N.of Kupang, Timor; Sunur Beach, Bali (all coll. McCausland); Morotai I,; N.of mouth of Mahakane river, E.Borneo (both AMS); PHILIPPINES: St. Cruiz I, Zamboanga; Baler, E.coast of Luzon (both ZMC); Guijulugan, Negros; Punta Princessa, Palawan; Cuyo I, Calamianes; off Basilan; Lemery, Luzon; Aindangan, Mindanao; Tagbayak Bay, Palawan; Tataan, Tawi Tawi group; Port Ciego, Balabac (all USNM); HONG KONG: (BMNH); RYUKYU IS.: (USNM); WEST IRIAN: Sowek, Soepiori, Schouten I (AIM); Biak (AMS); PAPUA NEW GUINEA: Manus I (ZMC); Palikau village, Mussan I, New Ireland; Rabarua, E.New Britain (both coll. Parkinson); Mongop, near Kavieng, New Ireland; Madang; Duke of York I, New Britain (all AMS); SOLOMON IS.: Gihili, Bougainville; Reef I, Santa Cruz group (both AMS); AUSTRALIA: Green I, Qld. (AIM); Port Curtis (AMS); Nth.Keppel I (coll. Gardner); NEW HEBRIDES: Kakula I, N.Efate I; Tuki Tuki Pt.,Efate I; Port Havannah, Efate I; Pango Pt., Efate I (all AIM); Hog Harbour, Santo I (coll. Taylor); Vila, Efate I; Surunda, Espiritu Santo (both coll.Cole); LOYALTY IS.: (AMS; USNM); NEW CALEDONIA: Bourail (AMS); FIJI IS: Levuka, Ovalau I; Vanua Balavu I; Lakeba I; Moce I; Karoni I, all Lau group (all AIM); Suva Pt.(USNM); Vabia, Ono I; Nadi Bay; Lautoka (all AMS); Nananu-i-Ra I (coll.Eker); Ogea I, Lau group (coll.Northgrove); TONGA IS: Tongatapu I (USNM); Nuku'alofa (ZMC); Haapai (coll. Eker). Fossil record. PLIOCENE: Akelamo valley, Obi I, Timor, Indonesia (Fischer in Wanner 1927); PLIO- PLEISTOCENE: Panay I, Philippines (Shuto 1969). When Linnaeus (1758) named the species Buccinum arcularia, he obviously had in mind the diminutive of arcula which is of feminine gender, rather than arcularius (the casket-maker) of masculine gender, and the species should be listed as Nassarius arcularia (Linnaeus). Occasional specimens from Sri Lanka, Nicobar Is, Andaman Is, Indonesia and the Philippines, have a reduced columellar callus which is horizontally truncate and some distance anterior to the body whorl suture .