Shell up to 15.0 mm in length but frequently only half this size, solid, elongate-ovate to almost squat, teleoconch of 4-6 convex whorls, protoconch of 2½-34 glassy, carinate, embryonic whorls; sculptured with few to numerous axial ribs which are either continuous to the back of the outer lip or become obsolete on the dorsal side of the body whorl; in some specimens spiral sculpture is almost absent on the spire whorls and only weakly indicated on the body whorl, while in others spiral striae are quite distinct in interspaces of all whorls; a shallow or moderately deep subsutural groove separates sutural nodules which are either low and rounded or distinctly echinate. Aperture moderately open, outer lip thickened and denticulate within, varix frequently swept upwards in profile, columellar callus moderately narrow and regularly convex but sometimes slightly spreading above parietal wall, col- umella denticulate, siphonal canal moderately short or slightly produced. White to cream in colour, usually ornamented with one row of reddish-brown spots in interspaces of sutural nodules, another row of spots adjacent to sutures on spire whorls and 2 additional interrupted reddish-brown bands on body whorl, columellar callus and aperture white. Operculum brown and usually with only 1 or 2 denticles on either side of margin. TYPE LOCALITY. Catbalonga, Samar I, 15 m (sinusigerus); Loo Choo Is Okinawa, Ryukyu (beata); Mauritius (cernica); Abyssinia (abyssinica); Reef 1, Kyuk Phon, off Arakan coast (aracanen- sis); off the coast of Pakistan, 25°N & 63°E, 46 m (collaticia); S.E. of Akik Seghir, Red Sea, 17°26'N & 39°19'E, 332 m (lathraia); Phoenix Bay, Andaman Is, 2-5 m (phoenicensis); St.306, Flores Sea, Indonesia, 8°27'S & 122°56.5'E, 247 m (brevis Schepman); Panay I, Neogene of the Philippines (greyanus).

The species is extremely variable in shape and sculpture, and end-members of the varietal chain could be easily mistaken for separate species. From all the material available to me, I have been unable to find a single diagnostic character of a constant nature by which I could distinguish two distinct biospecies. Schepman (1911) made the following comment on this species: "varying in nearly every respect, in size, shape (more or less elongate), number and development of ribs, some specimens be- ing nearly smooth on last whorls, others more or less closely ribbed, in colour, distinctness and breadth of the band. However, it is impossible for me to separate them." Bisacchi (1930) placed collaticia Melvill & Standen in synonymy of N.aracanensis E.A.Smith, while Tomlin (1940) placed aracanensis E.A.Smith, N.collaticia Melvill & Standen, and N.himeroessa Melvill & Standen, in synonymy of N.abyssinica (Marrat). I agree with Tomlin's synonymy but would exclude Nassarius himeroessus as a distinct species. N.sinusigerus occurs in 3 forms: the typical form sinusigerus A.Adams, which lacks spiral sculpture on spire whorls and only obsolete striae are present on body whorl, and the axial ribs have a tendency to become obsolete on the dorsal side of the body whorl, and the banding is weak and nebulous. Nassa beata Gould and Nassarius greyanus Shuto, belong to the typical form which occurs most frequently in the Indonesian-Philippine region. The form abyssinica is characterised by its distinct spiral sculpture and somewhat echinate sutural nodules. Nassa collaticia Melvill & Standen, and probably N.lathraia Sturany, belong to this form, while N.phoenicensis Preston, is intermediate between the typical sinusigerus and abyssinica forms, and usually occurs throughout the species range. The small, squat, striate aracanensis form occurs more frequently in the western Indian Ocean. Nassa sinusigera var. cernica G. & H.Nevill, does not appear to belong to N.sinusigerus on the basis of the type-figure which resembles N.delicatus (A.Adams) more so than N.sinusigerus. Nassa ovoidea var. brevis Schepman, is not the same species as Nassa ovoidea Schepman (= Nassarius idyllius Melvill & Standen), but is a small individual of the phoenicensis form of N.sinusigerus. Schepman's epithet is a primary homonym of Nassa brevis Bellardi, 1882.

DISTRIBUTION. From the Red Sea and the Gulf of Oman to Madagascar, India, the Ryukyu Is and the Fiji Is. In mud and muddy sand, subtidal, from 10-525 m. Material examined. RED SEA: Dahlak Archipelago, 15°18'N & 40°23'E, 27-110 m; Eilat, Gulf of Aqaba, 40-49 m; Ras-a-Tantur; El Hamira Bay, 30-47 m; off Mersat Abu Samra, 49-50 m; Taba, Gulf of Aqaba (all TAU); GULF OF OMAN: S.W. of Jask, 68 m (BMNH); PAKISTAN: Karachi (coll.Powell); MADAGASCAR: Tulear, 112 m (SMOM); INDIA: off Tranquebar, 11°06'N & 80°05'E, 28 m; off Ganges Delta, 20°49′N & 88°40′E, 75 m (both ZMC); SRI LANKA: Trincomalee (ZMC); N.W. coast of Sri Lanka, 9-307 m (AMS); ANDAMAN IS: Phoenix Bay (ZSI); MALAYSIA: Singapore (USNM); INDONESIA: Samalona, Macassar, Celebes, 35 m; Doelah, Kai Is, 50 m both (ZMC); Jamdena Str., E. of Wotap I, Tanimbar, 64-73 m; Teluk Dondinga near Ternate, Halmahera, 31-42 m; W.coast of Wasir I, W.Wokam, Aru I, 22-46 m (all WAM); Carita beach, N.of Labuan, W.Java (coll. McCausland); PHILIPPINES: off Mantataquin I, E. of Palawan group, 49 m; off S.E. Tawi Tawi, 33 m; N.E of Simonor 1, 17 m; off Tocanhi Pt., Tawi Tawi group, 90 m; N. of Corregidor 1, 681 m; off Arena Pt., Luzon, 525 m; off Jolo, 37 m; N. of Basilan, 143 m (all USNM); off Bantayan I, 55 m (coll.Nor- ton); RYUKYU IS: Okinawa (USNM); PAPUA NEW GUINEA: Port Moresby Bay, 10-15 m (ZMC); off wharf, Fairfax Harbour, Port Moresby, 15-18 m; S.W. of Yule I; Port Glasgow, 11 m (all AMS); Laing I, Hansa Bay, 35 m (coll.Tursch); SOLOMON IS: Kieta, Bougainville (coll. Whitehead); NEW HEBRIDES: Erakor lagoon, Efate I (coll. Willan); FIJI IS: Main Suva reef, Sth. Viti Levu (coll. Northgrove). Fossil record. PLIOCENE: Tjimantjeuri, S.Bantam, Java, Indonesia; PLEISTOCENE: Kajoeragi, Menado, Celebes, Indonesia (both Oostingh, 1939).