Range: Solomon Is., E. New Britain, Philippines, and S. India; local forms provisionally assigned to C. sertacinctus are known from Batangas Bay (Central Philippines), E. Flores (Indonesia), and from Marshall Is.

Description: Moderately small to medium-sized, moderately light to moderately solid. Last whorl ventricosely conical, sometimes slightly ovate; outline convex adapically, less so to straight below; left side occasionally slightly concave near base. Aperture wider at base than near shoulder. Shoulder subangulate to rounded, rarely angulate. Spire of low to moderate height, outline concave to sigmoid. Larval shell of 2-2.25 whorls, maximum diameter 0.8-1 mm. Teleoconch sutural ramps flat, often slightly convex in late whorls, with 0-1 increasing to 2-5 spiral grooves; grooves may be weaker on latest ramps. Last whorl with spiral ribbons on basal third to half; ribbons often distinctly narrower or sometimes replaced by ribs at anterior end. In shells from Flores (Pl. 40, Figs. 10, 11 ) , last whorl occasionally approaching conoid-cylindrical, with an almost straight right side centrally. Last whorl with spiral ribbons on basal half to sometimes two-thirds, split into narrow ribbons and/or ribs on anterior third. Shell morphology otherwise corresponding whith that of typical form. In shells from Batangas Bay (Pl. 40, Fig. 12), last whorl ventricosely conical or conoid-cylindrical; left side usually concave basally and right side often almost straight centrally. Shoulder subangulate. Teleoconch sutural ramps flat, with 0-1 increasing to 3-5 spiral grooves or 3 major and 3 minor grooves; grooves weak to obsolete in latest whorls. Last whorl with spiral ribbons below centre, narrower or split into narrow ribbons and ribs anteriorly. Shell morphology otherwise matching that of typical form

In typical form (Pl. 40, Figs. 4,5), ground colour white. Last whorl with 4 spiral bands of axially aligned brown spots and lines, below shoulder, on both sides of centre and at base; central bands broader and usually emphasized by pale beige underlying bands. Distinctly banded shells intergrade with immaculate shells. Larval whorls white to beige. Postnuclear sutural ramps with pale brown dots at outer margins and sparse light brown to brown radial lines and streaks. Aperture white or light yellowish to orangish brown deep within. In form solomonensis (Pl. 40, Figs. 6,7), ground colour white to bluish grey, variably suffused with brownish beige. On last whorl, beige shades usually arranged in 3-4 spiral bands, at base, on both sides of centre and often below shoulder. Basal bands usually fused, often all bands confluent. Spiral rows of brown to blackish brown dots, spots and axial streaks extending from base to shoulder, mostly restricted to 3-4 spiral zones with larger and more prominent markings overlying the beige background bands. Larval whorls and first 2-4 postnuclear sutural ramps brown to beige. Following ramps with white to blackish brown radial markings; marginal brown dots may be present. Aperture violet to bluish violet deep within, with brown to orangebrown collabral edge. A dark coloured form from Solomon Is. (Pl. 40, Figs. 8, 9, 13) differs from form solomonensis in having more prominent brown-beige background shades and a dark brown apex. Largely solid, coarse dark brown spiral lines extend from base to subshoulder area. Dark brown bars, flecks, and flames may cover most of the last whorl or may be absent. Radial markings on late sutural ramps larger and confluent Shells from Flores (Pl. 40, Figs. 10, 11) with a grayish violet ground colour. Last whorl pattern similar to that of typical C. sertacinctus but with prominent spiral rows of brown dots between the 4 spiral bands. Beige background bands absent. Apex white to grey; following sutural ramps with brown radial streaks and flames, without marginal dots. Aperture brown to bluish violet deep within, with a darker collabral edge. In shells from Batangas Bay (Pl. 40, Fig. 12), ground colour white to greyish violet or beige. Last whorl with 3-4 darker beige background bands overlain by brown to redbrown flecks, axial streaks and flames sometimes fusing into solid spiral bands. Intervening zones with a few spiral rows of similarly coloured dots, spots or bars. Apex pale brown to brown; following sutural ramps matching last whorl in colour pattern. Aperture brownish violet to violet deep within, with an orange-brown to brown collabral edge.

Periostracum pale olive-grey, thin, translucent, smooth. Periostracum grey; thin, translucent, smooth. Periostracum matching that of typical form.

Animal of form solomonensis beige-grey (Delsaerdt, 1993). In dark-coloured form from Solomon Is., foot greyish beige, mottled with dark brown on sole; dorsum with a blackish brown pre-marginal band latero-posteriorly. Tentacles white. Siphon brown or mottled grey and brownish beige, with blackish brown markings dorsally or dorsolaterally (Moylan, 1990). In specimens from Flores, animal uniformly pinkish white (Raybaudi & Ormas, 1992).

Habitat and Habits: Usually in 2-30 m, on sand; sometimes dredged as deep as 100 m. Specimens from Flores in 0.3-3 m, most common between 0.3-0.5 m, on fine white coral sand (Raybaudi & Ormas, 1992).

Discussion: C. sertacinctus resembles C. collisus, C. andamanensis, C. subulatus, C. broderipii, C. scalptus, and C. stramineus. C. collisus has a generally more conical last whorl (PMD 0.80-0.90), a more angulate shoulder, and a more prominent spiral sculpture on its late sutural ramps. C. andamanensis tends to have a conical or conoid-cylindrical rather than ventricosely conical last whorl, its spire outline is concave rather than sigmoid, and its last whorl pattern comprises small scattered markings. C. subulatus differs in its narrower last whorl (RD 0.51-0.54), more angulate shoulder, and its slightly concave late sutural ramps with a more prominent spiral sculpture. C. scalptus is smaller (to 28 mm), has more prominent spiral sculture on the late sutural ramps, and the spiral lines on its last whorl are finer than those of dark-coloured C. sertacinctus from Solomon Is. Typical C. broderipii can be distinguished by a generally lower spire with a concave rather than sigmoid outline, a generally more angulate shoulder, the absence of beige background shades, and by a last whorl pattern of typically 3 instead of 4 spiral bands. The population from Philippines provisionally assigned to C. broderipii and the population from Batangas Bay provisionally assigned to C. sertacinctus are closer in shape and colour pattern; they can be separated by the dashed spiral lines on the last whorl of the shells assigned to C. broderipii and by their white to beige apex. For comparison between C. sertacinctus and C. stramineus, see the Discussion of the latter species. The description of C. sertacinctus was based on shells from Guadalcanal, Solomon Is. (Pl. 40, Figs. 4, 5) that we provisionally consider a light colour variant of the more common form recently described as C. solomonensis (Pl. 40, Figs. 6, 7). C. sertacinctus form solomonensis has a relatively wide geographical range from Solomon Is. and E. New Britain to Philippines and India. Dark coloured shells from Solomon Is. (Pl. 40, Figs. 8, 9, 13) and from Marshall Is. are so similar to typical C. sertacinctus and form solomonensis in shell characters and animal colour that we regard them as a colour pattern variant of the same species. The shallow-water population from Flores (Pl. 40, Figs. 10, ll) is provisionally assigned to C. sertacinctus, because its shells are similar in colour pattern and unseparable by morphology. However, differences in the colour patterns of shells and animals suggest at least separation as a local race. Although the shells from Batangas Bay (Pl. 40, Fig. 12) are provisionally assigned to C. sertacinctus, a conclusive taxonomic placement of this population between C. broderipii and C. sertacinctus depends on further research.