Gyriscus: Shell small, trochiform, with a rounded body-whorl, spirally grancse sculpture, a narrow umbilicus, and a distinctive operculum that is flat, multispiral, circular, with a central nucleus; horny on the outside, but calcified internally, with a raised edge and a central pointed peg, the whole resembling a drawing-pin or thumbtack. The type species is a deep water Mediterranean shell.

Shell rather small, solid, lenticular, strongly sculptured with spiral cords, two of which usually form peripheral carinae. All of the cords are transversely deeply incised by spiral grooves.

Shell turbinately elevated, or in some instances planorbiform ; umbilicus typically moderate to wide, perspective, its margins slightly crenulated ; lip and columella simple. Operculum corneous, typically conically elevated, externally spiral, of numerous volutions, margined by projecting edges ; internal face smooth, bearing a spirally twisted median projection.
Distribution.—World-wide, tropical and subtropical seas.
Fossil.—Tertiary.

Teleoconch; very small to large (usually 5-12 mm, rarely over 30 mm), almost disk-shaped to tall roundly cone-shaped, with very narrow (Gyriscus) to extremely wide umbilicus (Torinista, Teretropoma); whorls weakly to distinctly bulging; sculpture: distinct axial (growth) sculpture crossing spiral ribs on entire surface; apical side: subsutural rib, 1-3 midribs and upper peripheral rib usually ± equally developed; midribs, occasionally also upper peripheral ribs fused (Torinista spp.); periphery formed by 2 in most cases ± equally strong ribs (LPR and IPR), between them often additional weaker spiral ribs; upper point of whorl attachment at lower peripheral rib, infraperipheral rib, or between them; base with 5-6 main spiral ribs, increasing in width towards umbilicus; innermost basal rib (UC) surrounding umbilicus with ± coarse nodules; in some species (Teretropoma, Gyriscus) fine additional ribs between main ribs on entire surface; umbilical wall usually with 1-2 narrow spiral ribs; coloration usually of distinct flecks and flames in brown or black on lighter, often white background* Protoconch: very small to large (0.55-1.4), distinctly heterostrophic, rarely with anal keel. Radula: five-toothed-taenioglossate; rachidian with strong central cusp flanked by numerous (6-22) smaller cusps on either side; inner and outer marginals with 4-13 cusps each. Operculum: horny, round, almost flat to tall cone-shaped, with pointed, peg-like projection on body side; peg not reinforced by external callus.

Descriptions of Subgenera:
- Subgenus Heliacus (Heliacus) ORBIGNY in SAGRA, 1842
Teleoconch: small to medium-sized (usually 6-13 mm, rarely over 20 mm), depressed to tall roundly cone-shaped, with narrow to very wide umbilicus (ca. 8-40% of shell diameter); whorls weakly to distinctly bulging; sculpture: spiral ribs with relatively large nodules on entire surface; number of ribs constant, only between lower peripheral and infraperipheral ribs occasionally with 1 ± strong additional rib; apical side: subsutural rib, single midrib (or two narrow ones) and upper peripheral rib usually equally developed, rarely upper peripheral rib somewhat stronger; periphery formed by lower peripheral rib and only slightly weaker infraperipheral rib (occasionally with additional rib between them); upper point of whorl attachment at or below lower peripheral rib; base usually with 5 spiral ribs, increasing in width towards umbilicus; umbilical wall usually with 1-2 strong, narrow spiral ribs; coloration of (in most cases distinctly demarcated) brown to black flecks and flames on ± white background, with peripheral ribs as a rule with very regular pattern; subsutural rib, infraperipheral rib and rib surrounding umbilicus (UC) often lighter colored. Protoconch: very small to medium-sized (0.55-1.05), distinctly heterostrophic, without anal keel- Radula: five-toothed-taenioglossate; rachidian with strong central cusp flanked by numerous (12-20) smaller cusps on either side; inner and outer marginals with 5-13 cusps each. Operculum: horny, round, cone-shaped, with peg-like projection on body side.

- Subgenus Heliacus (Pyrgoheliacus) BIELER, 1987
Teleoconch: very small to small (usually 2.6 to 8 mm), tall cone-shaped (in large specimens, height ± equals diameter), with narrow to moderately wide umbilicus (ca. 10-20% of shell diameter); whorls distinctly bulging, periphery rounded; sculpture: spiral ribs with ± rounded nodules on entire surface; apical side: subsutural rib, and 1-2 midribs of about equal strength, upper peripheral rib more prominent and sometimes (turritus) already part of the periphery; periphery otherwise formed by ± equally strong lower peripheral rib (most prominent part of periphery), strong infraperipheral rib, and an almost equally strong additional rib between them (here upper point of whorl attachment); suture distinct; base with 6 spiral ribs, increasing in width towards umbilicus, innermost somewhat sunken into umbilicus; umbilical wall bulging, with or without weak spiral threads; coloration off-white to yellowish-tan; peripheral ribs with pattern of brown flecks (pattern corresponding between various ribs); inner lip off-white to dark brown. Protoconch; small to medium-sized (0.82-0.98), distinctly heterostrophic, with or without anal keel. Radula: five-toothed taenioglossate; rachidian with strong central cusp flanked by smaller cusps on either side; inner and outer marginals with several cusps each (Atlantic H verdensis). Operculum: horny, round, cone-shaped, with peg-like projection on body side.

- Subgenus Heliacus (Torinista) IREDALE, 1936
Teleoconch; very small to medium-sized (usually 3-12 mm), in most cases disk-shaped with weakly bulging whorls, occasionally depressed cone-shaped; umbilicus very narrow to extremely wide (ca. 9-55% of shell diameter); sculpture: spiral ribs with ± fine nodules, often flattened on the midribs; distinct axial sculpture in forms with fused spiral ribs; apical side: subsutural rib usually somewhat wider than following (often fused) midrib; periphery formed by somewhat stronger lower peripheral rib and infraperipheral rib, between them often 1-2 ± strong additional ribs; upper point of whorl attachment at lower peripheral rib, infraperipheral rib, or between them; base usually with 6 spiral ribs, increasing in width towards umbilicus; umbilical wall smooth except for axial growth lines, or with 1-2 ± demarcated spiral ribs; coloration of usually irregular flames in various shades of brown on apical and basal sides, only peripheral ribs often with regular pattern of light and dark brown flecks; innermost rib on base (UC) in most cases light in color. Protoconch: small to large (0.65-1.40), distinctly heterostrophic, in most cases with several folds in false umbilicus, rarely with anal keel. Radula: five-toothed taenioglossate; rachidian with strong central cusp flanked by numerous (6-20) smaller cusps on either side; inner and outer marginals with 6-10 cusps each. Operculum; horny, round, cone-shaped (often taller than diameter), with peg-like projection on body side.

- Subgenus Heliacus (Grandeliacus) IREDALE, 1957
Teleoconch: shell small to large (usually 9-33 mm); small shells with angular periphery and basal area more convex than apical side; larger shells with rounded periphery and bulging whorls; umbilicus moderately wide to wide (ca. 17-36% of shell diameter); sculpture: on early whorls, subsutural rib and 2 midribs ± weakly developed and upper peripheral rib prominent (concave area between upper and lower peripheral rib); on later whorls, subsutural rib stronger, or subsutural rib, midribs and upper peripheral rib nearly equally strong (often additional rib between upper and lower peripheral rib); periphery: early whorls two-ribbed, with somewhat more prominent lower peripheral rib and infraperipheral rib; later, 1-3 additional spiral ribs between them, one of which often equally prominent; upper point of whorl attachment at lower peripheral or additional rib; base with 6 (later 7) spiral ribs, increasing in width towards umbilicus; large specimens with additional finer ribs interspersed; umbilical wall usually with 1-2 fine spiral ribs; coloration yellowish tan, early whorls often darker; peripheral ribs sometimes with fleck pattern. Protoconch: small to medium-sized (0.78-1.20), distinctly heterostrophic, without anal keel. Radula: five-toothed-taenioglossate; rachidian with central cusp flanked by numerous (9-22) cusps on either side, with central cusp larger than or equal to flanking cusps; inner and outer marginals with 6-10 cusps each. Operculum; horny, round, flat in young individuals, later moderately cone-shaped, with peg-like projection on body side.

- Subgenus Heliacus (Teretropoma) ROCHEBRUNE, 1881
Teleoconch: small to medium-sized (usually 5.5-13 mm); depressed to turreted cone-shaped, always with distinctly rounded whorls; young or depressed shells with two-ribbed periphery; umbilicus moderately wide to extremely wide (23-65% of shell diameter); sculpture: axial growth sculpture on entire surface; apical side: subsutural rib, single midrib, and upper peripheral rib ± equally strong developed, at least in fully grown specimens interspersed with finer spiral threads; periphery formed by almost equally strong lower peripheral and infraperipheral ribs, always flanked by additional weaker ribs; upper point of whorl attachment at infraperipheral rib under formation of a usually deep suture; base with ca. 6 stronger spiral ribs (with usually one weaker additional rib between them); basal area angular or rounded at umbilicus; with spiral sculpture on the umbilical wall; white, solid brown, or with ± irregular flames of tan or reddish to dark brown, with periphery and umbilicus often lighter. Protoconch: small to large (0.72-1.24), distinctly heterostrophic, without anal keel. Radula: five-toothed-taenioglossate; rachidian with strong central cusp flanked by numerous (9-14) smaller cusps on either side; inner and outer marginals with about 7 cusps each. Operculum: horny, round, moderately cone-shaped or flat to concave, with peg-like projection on body side.

- Subgenus Heliacus (Gyriscus) TIBERI, 1867
Teleoconch: small (usually 6-10 mm); tall, roundly cone-shaped with distincdy rounded, bulging whorls; umbilicus very narrow to narrow (ca. 5-10% of shelldiameter); entire surface with fine granular sculpture formed by crossing fine axial growth threads and narrow spiral ribs; later whorls with many additional spiral ribs which are almost as strong as the main ribs; apical side: subsutural rib, two midribs, upper peripheral rib, and several additional ribs interspersed; broad, rounded periph¬eral region demarcated by lower peripheral and infraperipheral rib, with 1-4 ± strong and sometimes numerous weaker, additional ribs between them; upper point of whorl attachment between upper and infraperipheral ribs, at additional ribs of periphery; no distinct suture; base with 6-8 stronger and numerous finer spiral ribs; umbilical wall usually with 1-2 ± irregular spiral ridges, in large specimens often smooth except for growth lines; usually white, occasionally with weak tan flames and brown parietal wall. Protoconch: medium-sized (0.90-1.15), distincdy heterostrophic, protruding bubble-like, without anal keel. Radula: five-toothed-taenioglossate; rachidian with strong central cusp flanked by numerous (10-12) smaller cusps on either side; inner and outer marginals with 4-8 cusps each [Mediterranean H jeffreysianus]. Operculum; horny, round, weakly cone-shaped, with peg-like projection on body side.