Nassarius siquijorensis is a rather variable species which may exceed 40 mm in height. The Thai specimens are characterized by 1) elongate-ovate shell with slightly cyrtoconoid spire, 2) weakly canaliculated sutures, 3) rectangular, low and oblique subsutural nodules and 4) sculpture of slightly prosocline, slender ribs and of spiral grooves in the furrows between ribs; 39 ribs occur on the penultimate whorl, 36 on the body whorl where they tend to fade away toward the aperture. According to CERNOHORSKY (1984), Nassarius siquijorensis is distinguished from Nassarius castus (Gould, 1850) by having more numerous axi-als and canaliculated sutures. DISTRIBUTION AND HABITAT. The species is distributed in the tropical Indo-Pacific, from the Red Sea to New Caledonia and northward to Japan. It occurs in the sublittoral and upper bathyal zones, dwelling in fine sandy and muddy bottoms. Nassarius siquijorensis was noted to occur abundantly in Tolo Channel, Hong Kong, and regarded as a generalist feeding species, tolerant of broad fluctuations in environmental conditions (TAYLOR & SHIN, 1990).
FOSSIL RECORDS. Late Middle Miocene to Quater-nary of Indonesia; Holocene of Thailand. The possible presence in Pliocene and Quaternary de-posits of the Philippines and Taiwan needs to be confirmed.

Shell up to 43.0 mm in length, elongate-ovate to almost ovate, spire produced, teleoconch of 6-8 convex whorls, protoconch of 3%-3% glassy, carinate embryonic whorls, upper spire whorls occasionally angulate, sutures usually prominently canaliculate, some individuals with only weakly channelled sutures; sculptured with numerous, slender and occasionally slightly oblique axial ribs which either continue to the back of the outer lip or become obsolete on the last 1-2 whorls; axial ribs, when present, number from 30-50 on the body whorl and from 34-52 on the penultimate whorl; spiral sculpture consists of very fine spiral threads which are either confined to the interspaces or weakly override axial ribs, and number from 5-9 on the penultimate and from 0-14 on the body whorl, apart from 6-8 slightly nodulose cords at the base and 4-7 oblique cords on the siphonal fasciole, sutural nodules well defined in ribbed specimens or with only a subsutural groove in smooth individuals, spiral sculpture occasionally obsolete. Aperture moderately narrow, outer lip thickened and variced, interior with 11-18 lirate denticles, edge of outer lip either simple or with up to 18 small spinose den- ticles, columellar callus moderately narrow but occasionally flaring over siphonal fasciole and thinn- ing above parietal wall, columella with 5-15 small denticles or wrinkles, siphonal notch and anal canal prominent. Cream, grey, fawn or light brown in colour, some specimens with 1-3 faint or distinct brown bands on body whorl, bands frequently only visible as short brown bands on the dorsal side of the body whorl, columellar callus white, interior of aperture greyish-brown, denticles paler. TYPE LOCALITY. Siquijor I, Philippines (siquijorensis); none (canaliculatum Lamarck; crenellifera; cingenda); near Lith, Red Sea, 39°29'E & 19°57'N, 430 m (steindachneri); Timor, Pliocene of In- donesia (teschi); Niki Niki, Timor, Pliocene of Indonesia (marinuensis); Toi Oesapi Soka, Timor, Pliocene of Indonesia (timorensis); off Isshiki, Aicho Prefecture, Honshu, Enshu-nada, Japan, 200-300 m (hirasei). DISTRIBUTION. From the Red Sea to India, Mauritius, Japan and New Caledonia. In sand, subtidal to a depth of 450 m. Type specimens. Three syntypes of N.siquijorensis (A.Adams), are in the British Museum (N.H.), London, No.1973118, and the specimen measuring length 24.0 mm, width 11.6 mm, is here selected as the lectotype (pl.25, fig.12). The holotype of Nassa crenellifera A.Adams, is in the same Institu- tion, No. 197329, length 19.3 mm, width 10.3 mm, and the holotype of N.cingenda Marrat, is in the Merseyside County Museum, Liverpool, length 30.0 mm, width 15.5 mm. The holotype of Nassarius hirasei Kuroda & Habe, is in the National Science Museum, Tokyo, No.48261, length 25.5 mm, width 14.8 mm, and syntypes of Buccinum canaliculatum Lamarck, are in the Museum d'Histoire Naturelle, Geneva, No.1101/96, length 36.4 mm and 35.0 mm respectively. Types of N. teschi Koperberg, N.marinuensis Koperberg, and N.timorensis Koperberg, are probably in the Geology Department, University of Amsterdam, and the types of N.steindachneri Sturany, can no longer be found in the Natural History Museum, Vienna (Dr. E.Wawra, in litt.). Material examined. RED SEA: opposite marine laboratory, Eilat, Gulf of Aqaba, 400-450 m (TAU); EAST AFRICA: S. point of Grand Recif, Comoro Is, 400 m (MNHNP); MAURITIUS: (AMS); INDIA: Karvar (USNM); Madras (AMS); SRI LANKA: (USNM); N. coast of Sri Lanka (AMS);j THAILAND: Koh Kong, 18-27 m; Kohl Kut, 27 m (both ZMC); W. coast of Tarutao I, Satun, 12 m (PMBC); Phuket town, Phuket (coll. Richardson); MALAYSIA: Batu Ferringhi, Penang; Pulau Langkawi, Kedah (both coll.McCausland); INDONESIA: Pruput, Bantam; Keledjitan, Bantam, Java; S. of Dodepo I, Gulf of Tomini, Celebes; S.E. of Tikola, Buton Str., Celebes,68 m (all USNM); Lampong Bay, 5°42'S & 103°17'E, 29 m (ZMC); Labuan, Sarawak, Borneo (coll. Richard- son); PHILIPPINES: off Adyagan I, E.Masbate, 247m; N. of Dumurug Pt., Masbate, 249 m; off Sibugay 1, E. of Masbate, 198 m at 15.5°C; Tintag I; Malampaya, Palawan group, 13 m; Cebu City; Lama, Zamboanga; Manila Harbour; Mindanao; Santa Cruz I, Zamboanga; N. of Corregidor, 68 m; Daram Channel, W. Samar, 48 m; Juijulugan; off Jolo, 37 m; Leyte; off Ptago, Luzon (all USNM); Tayabas Bay; Punta Engano, Mactan I, Cebu (both coll. Dan); Ligtang, Rosario, Carite, S.tip of Manila Bay (coll. Deynzer); off Batangas, 14°27'N & 120°41.5'E, 36-37 m (MNHNP); CHINA: Amoy; Hongkong, 7-22 m; Foochow; Yenking, Checkiang Pro- vince; off Pratas 1, 124 m (all USNM); Lamma I, Hongkong; off Wong Chuk Kok, 33-40 m; Cheng Chow I; Lantow I; Aberdeen, all Hongkong (all AMS); RYUKYU IS: Buckner's Bay, Okinawa (coll. Choslen); JAPAN: Mikawa, 92 m (USNM); NEW CALEDONIA: Poindimie (AMS); S. Point of Great reef, 400 m (MNHNP). This species can be separated from N.castus (Gould) on features of more acuminate spire, canaliculate sutures and considerably more numerous axial ribs (0-27 in castus and 0-52 in siquijoren- sis on the penultimate whorl). The typical form siquijorensis A.Adams, is the form with prominent axial ribs all the way to the back of the outer lip. N. cingenda Marrat and N.crenellifera A.Adams, also belong to this form, except that in the latter the axial ribs are finer and even more numerous. The form hirasei Kuroda & Habe, is also fully ribbed but is squatter, with the body whorl more inflated. In the form canaliculata Lamarck (a primary homonym), the last 1-3 whorls are almost smooth except for a few basal striae and occasionally a subsutural groove or spiral thread. It is this form which has been confused with Nassarius dorsatus (Roeding), a species endemic to Northern Australia, and easily separable on shell-features from N.siquijorensis.