Shell thick, solid, very short or annular, open at both extremities; equivalve, equilateral, angular and sharp anteriorly, only slightly touching by the opposite edges; hinge obsolete; a considerable internal spoonlike cavity; one slightly sensible muscular impression.
Tube more or less distinct from the substance in which the animal lives, cylindrical, straight or flexuous, closed with age at the oral extremity so as to envelop the animal and its shell; always open at the other end, and divided interiorly into two syphons by a middle partition.
Teredo navalis.
T. palmulata.
T. gigantea.
T. navalis. The common Ship Worm.
Species very thin, cylindrical, and smooth; slightly twisted, white, finely striated longitudinally.
FAMILY II.
Pholadaria. Two genera.
1. Pholas. The Stone Piercer. Nine species.
This genus is without any tubular sheath; it derives its name from the Greek word φωλεω, to hide, alluding to the custom of its inhabitant in forming cells in rocks, wood, &c.