Circular, hut ventrally flattened, white to gray with brown patches and irregularly commarginal bands, with 20-40 coarse rounded radial ribs crossed by fine commarginal striae, periostracum inconspicuous, umbones orthogyrate; interior white with brown stain. New Jersey to Florida, Bermuda, Bahamas, West Indies, Gulf of Mexico, Caribbean Central America, South America (to Brazil). Length 20 mm (to 31 mm). Formerly in Glycymeris. Compare Tucetona subtilis which is ventrally rounded and has more radial ribs.

Tucetona pectinata (Gmelin, 1791) Distribution: North Carolina to Florida, Texas; Brazil. Size: 12 to 25 mm (1/2 to 1 in). Comb Bittersweet Description: Color grayish with reddish-brown maculations, interior with brownish coloration bleeding through; shape subcircular; sculpture thick with raised, modular radial ribs crossed by fine commarginal growth lines; hinge line broad and arched; lateral teeth on both sides of umbo chevron shaped, semi-erect in central area; ventral margin with broad crenulations. Habitat: Calcareous environments at depths from 24 to 110 m (80 to 360 ft). Remarks: Most Texas records are confined to single valves found on beaches and the FGB. See Odé (1978c); Mikkelsen and Bieler (2008). Synonym: Glycymeris pectinata (Gmelin, 1791).