Common Name

"Bilious Cone"

Status

Regarded as a valid species.

Type Locality

Not mentioned, designated (Coomans, Moolenbeek & Wils) Gulf of Mannar, between India and Ceylon (Sri Lanka)

Distribution

S. Africa to Somalia and to India and Sri Lanka, absent from Red Sea and Persian Gulf; Indonesia to Philippines and to Papua New Guinea, Solomon Is. and Queensland

Maximum Reported Size

55 mm

Description

Moderately small to moderately large, moderately light to solid. Last whorl conical, ventricosely conical or broadly and ventricosel y conical, occasionally pyriform; outline variably convex at adapical fourth to half and straight to moderately concave below; left side often sigmoid. In Indian populations, last whorl most conical, RD most variable. Shoulder angulate to subangulate, distinctly tuberculate to irregularly edged. Spire of low to moderate height, outline slightly concave to slightly convex. Posmuclear spire whorls variably tuberculate. Teleoconch sutural ramps almost flat, with 1 increasing to 4-7 spiral grooves; spiral sculpture may be weak in last whorls. Entire last whorl with rather evenly spaced, wrinkled spiral ribs and alternating wrinkled threads; spiral sculpture may be weaker toward shoulder, and some specimens are quite smooth.

Ground colour pale greyish blue or pale pink. Last whorl spirally banded with tan to olive brown or orangish brown, usually with variably broad ground-colour bands at centre and shoulder. In Indian Ocean populations (Pl. 5, Figs. 1 -8), last whorl often maculated with bluish brown axial streaks; overlying spiral rows of brown dots sparsely to heavily developed on ribs. Basal part of last whorl and columella dark brown; in Indian shells (Pl. 5, Figs. 1,3,4), basal part mostly orange or tan, often similar to adjacent parts. Apex light brown or pink. Teleoconch sutural ramps radially maculated with orange to blackish brown, varying from sparse spots between marginal tubercles to solid dark brown colouration. In small adults, aperture bluish violet, edged with brownish violet, with a pale central band and a translucent marginal zone; aperture white in large adults.

In Indian shells, periostracum brown or yellowish brown, variably thick, slightly translucent to opaque, with about 20 variously arranged tufted spiral ridges.

Dorsum of foot brown or black anteriorly, with a red distal edge; sides of foot reddish brown, flecked with white dorsally; sole and ventro-lateral edges of foot red. Rostrum reddish brown, red distally. Tentacles light brown to red. Siphon reddish brown dorsally, edged with pale red distally (Indian animals, Kohn, 1978a & unpubl. observ.). In Indonesian and W. Pacific animals, foot and siphon brownish red dotted with black; with sparse white dots on siphon. Sole serration, of foot and siphon may also be light red, with thin transverse I brown lines on the dorsal side of siphon. Rostrum and tentacles dark red to brown (Chaberman, pers. comm., 1981; Kohn, unpubl. observ.) (Pl. 74, Fig.7).

Habitat & Habits

Intertidal and slightly subtidal. In Mozambique and South Africa, at and below low-tide level in sandy crevices and caverns (Kilbum & Rippey, 1982; Grosch, pers. comm., 1989). Some Indian populations occupy small caves and associated tidal pools on terraced intertidal limestone benches (Kohn, 1978a). In Indonesia, on intertidal to slightly subtidal benches of truncated reef limestone, on varied hard and soft substrata (Kohn & Nybakken, 1975). In N. Papua New Guinea, common on exposed shallow reefs (Chaberman, pers. comm., 1981); more frequently found on extensive mud flats of mainland habitats than on coral reef in E. Australia (Huish, 1978). The species is known to prey on eunicid and nereid polychaetes (Kohn & Nybakken, 1975; Kohn, 1978a). In Queensland, C. biliosus deposits small, stocky egg capsules underneath rocks near the reef crest (Loch, pers. comm., 1987). In Pakistan, number of eggs per capsule is 100- 1,410; egg diameter of 160- 180 µm, predicts a miminum pelagic period of 27-25 days (Zehra, 1990; Perron & Kohn, 1985; Zehra & Perveen, 1991).

Discussion

C. biliosus is most similar to C. hyaena. For the distinctions between them, see the Discussion of the latter species. The South Indian population is distinctive in its size and colour, but shows no clear differences in other shell characters. Walls ([1979]) described populations from South Africa and Mozambique (Pl. 5, Figs. 5, 6) as a separate subspecies (C. b. meyeri). These shells tend to be smaller than Indian shells and have a more convex outline of the last whorl, and more often weak tubercles. However, they intergrade with shells from southern India and the differences in shell morphometry are minimal. Our results suggest a clinal variation, in agreement with Kilbum (1982). C. biliosus refers to a specimen from the Gulf of Mannar, India, C. punctatus and Kem>C. piperatus

seem to be synonyms. C. biliosus f. neoroseus is based on a specimen assumed to be from Philippines (da Motta, 1993); similar shells from Indonesian populations are also known. Specimens matching the lectotype of C. parvulus are known from Philippines and the W. Indian Ocean. C. imperator represents the Queensland population.).

References

• Mus. Bolten 2: p 39, no 489/15, not figured.