Lithophaga bisulcata: Elongated cylindrical, inflated, umbones near (but not at) anterior end, thin-walled, whitish with yellow-brown periostracum and calcareous incrustation that projects bluntly beyond posterior margin, smooth with radial groove dividing valve into two sections, ventral half with periostracal pits (most visible in juveniles); interior yellow-brown with purplish tint, margin smooth; living bored into soft rock or dead coral. North Carolina to Florida, Bermuda, Bahamas, West Indies, Gulf of Mexico, Caribbean Central America, South America (to Uruguay). Length 45 mm. Compare other Lithophaga species (L. antillarum and L. nigra do not have calcareous posterior extensions, whereas those of L. aristata cross scissorlike), and Coralliophaga coralliophaga, which is whiter and thicker shelled with heterodont hinge teeth.

Lithophaga bisulcata (d'Orbigny, 1853) Mahogany Date Mussel Distribution: North Carolina to Texas-Louisiana; Bermuda; Brazil. Size: 25 to 43 mm (1 to 170 in). Description: Color brownish-mahogany, inner surface purplish-gray; shape elongate-oval; sculpture of commarginal growth lines; posterior portion of valve separated from frontal slope by a distinct channel that extends exteriorly from umbo to ventral margin; anterior slope divided into 2 sections by a second channel that extends marginally from umbo to ventral margin; shell covered with a grayish-brown encrustation. Habitat: Bores into oysters, rocks, and coral. All along Texas-Louisiana coast at depths from 0 to 417 m (1370 ft). Remarks: See Turner and Boss (1962); Ogle (1976).