Small to medium-sized, high-spired cone-shaped shell with narrow to wide umbilicus, distinctly angular at base; upper-side sculpture of 3 almost identical ribs with more or less flattened nodules; double keel formed by 2 ribs, with the lower one weaker, basal sculpture of 5 very regular spiral ribs; umbilical side of columellar wall with 1 strong spiral rib. White. Protoconch diameter 0.88-1.02 mm, distinctly heterostrophic, without anal keel.
Teleoconch: small to medium-sized, diameter of specimens in collections usually 8-13 at 4 1/2-5 5/8 whorls (rarely over 15.0 with more than 6 1/2 whorls). Shape: high-spired cone-shaped with narrow to wide umbilicus (UD ca. 13-32% of SD, x = 19%); distinctly angular at base. Sculpture: Upper side: SSR, single MR and UPR almost identical, with ± flattened nodules; Periphery: double keel formed by LPR and IPR, with IPR weaker; upper point of whorl attachment between LPR and IPR, suture shallow; Base: 5 very regular spiral ribs, somewhat increasing in width towards umbilicus, innermost forming UC; UC with 9-19 nodules on body whorl; umbilical side of columellar wall with 1 strong spiral rib. Coloration: greyish-white to pure white; sometimes with light-tan, somewhat translucent square blotches on upper side (numbering 7-23 on body whorl, x = 13), and orange lines in grooves between spiral ribs. - Protoconch: small to medium-sized (0.88-1.02, x = 0.94), multispiral, distinctly heterostrophic, without anal keel; white with brown outer corners of peritreme and 1 small brown fleck close to highest point of apex. - Periostracum: greyish-white, thin; usually only retained in grooves between spiral ribs and on umbilical wall. -Operculum: as described for subgenus. - Radula: five-toothed taenioglossate (2-1-2); rachidian tooth stronger than marginal teeth, with prominent, pointed median cusp flanked by about 12 smaller, blunt cusps; marginal teeth longer, curved and forked with 6-10 tapering cusps (see THIELE, 1925a: 113, pl.46 fig.16). - Anatomy: not studied. - Soft-body coloration of living animal: milky white to salmon-colored (not correlated with presence/absence of shell pattern); anterior foot and upper side of tentacles weakly speckled with small black chromatophores, few embedded white granules (pers. obs., South Africa).

Height, 6 mm; diameter, 8 mm. Shell: trochiform, with sharply angled whorls; cream with darker interrupted bands. Spire: four rather flat -whorls; suture not distinguishable. Sculpture: closely set, finely beaded spirals, the periphery of each whorl marked by a spiral of larger beads. Aperture: subquadrate; outer lip indented by spiral sculpture. Base: sculpture like that of dorsum; umbilicus wide and deep, bordered by a crenulate spiral. Color: ashy gray with darker marks and creamy spirals around the sutures.
Specimens are occasionally found with H. variegatus and H. mighelsi in beds of the sea anemone Palythoa but are uncommon.
H. trochoides occurs throughout the Indo-West Pacific from Ceylon to southern Japan and the Caroline and Society islands, and is recorded from Ecuador (Robertson, 1976).

Heliacus trochoides is readily distinguished from other species in this group by its overall white, conical shell. Other white forms with which it could be confused, are H. (Teretropoma) mighelsi PHILIPPI (with a rounded peripheral area formed by two almost identical ribs that are flanked by weaker threads), and H (Gyriscus) asteleformis POWELL (with a much finer sculpture including at least five spiral ribs on the upper side of the shell).

Geographical distribution: From the African southeast coast to the central Pacific. Also reported from mainland Ecuador, east Pacific (ROBERTSON, 1967).
Habitat & Habits/feeding behavior: As described for H variegatus (see P1.2 Fig.E). ROBERTSON (1967) reported it to feed on Palythoa tuberculosa (ESPER) in the Maldive Islands, and Palythoa vestitus (VERRILL) in the Hawaiian Islands.