Type species: Lithodomus lithophaga Linne 1758.
Shell sub-cylindrical, very inequilateral; anterior end rounded, posterior end rostrate or cuneiform; umbos anterior, not much produced; hinge plate linear, without teeth; ligament marginal, internal; periostracum persistent; interior with a thin nacreous layer; outer layer of shell of tubular structure.
Distribution: The genus is represented in warm seas of the principal oceans in both northern and southern hemispheres.
Remarks: The young shells are fixed by their byssus, but later they begin to bore into shells and rocks, in which the animal forms flask-shaped excavations. Casts are often found in the fossil state. The animal is phosphorescent.

Lithophaga Röding, 1798. Type species (M): L. mytuloides Röding, 1798, Mytilus lithophagus Linnaeus, 1758. Recent, Mediterranean. Lithophagus Megerle von Mühlfeld, 1811. Type species (M): L. communis Megerle von Mühlfeld, 1811, Mytilus lithophagus Linnaeus. Lithodomus Cuvier, 1817. Type species (M): Mytilus lithophagus Linnaeus.. Shell elongate, cylindrical. Umbones anterior. Sculpture absent, or of weak oblique striae. Posterior slope frequently with ridges or radial riblets. Periostracum thick, adherent, generally with calcareous incrustations. Ligament external, elongate, usually sunken into groove and attached to resilial ridge. No byssal gape. Seven living subgenera are recognized, based on the presence and structure of the external incrustations, and these can be correlated with some anatomical differences. The genus is known from the Jurassic, but is probably much older. Recently settled young are byssally attached, but quickly start to bore into the substratum, usually shell or rock. The bore holes are spacious, tapered chambers with a narrow exit. Except in Lithophaga, s.s., calcareous incrustations form a posteriorly directed process that protects the bore hole entrance. Lithophaga, s.s., which lacks calcareous incrustations, is not represented in the northeastern Pacific, but three subgenera are present. The name is derived from the Greek lithos, a stone, and phago, to eat; the gender is feminine.