Shell irregularly oval, with one and a half to two whorls, the nuclear whorl smooth and very distinct from the rest of the shell; growth lines rough, sometimes a little imbricated; the surface is generally covered with subspiral lines of erect, prickly, often tubular scales; growth lines of the shelf finely marked, and with the edge of the shelf shaped something like a horizontal brace. Color whitish, variegated with brown; the shelf white, with translucent lines.
Length, 28; breadth, 21; height, 10 mm.
Arroyo and off Point Melones, Porto Rico. Distributed almost universally throughout the warm seas of the globe. Young specimens of one or two other species were obtained by the Fish Hawk expedition, but not in condition to be satisfactorily named.

Crepidula aculeata (Gmelin, 1791). Length, 18 mm; diameter, 13 mm; height, 4 mm. Shell: oval, low, domelike; apex lateral and posterior; columella expanded as a shelf which covers the posterior half of the aperture. Sculpture:
radiating ribs, some of which may be roughened. Color: variable — yellow or brown, often with brown rays. Animal: uniform buff, head and mantle with opaque white spots; posterior portion of the foot attached to the shell but the anterior section is extremely mobile and the animal can right itself by means of its extended foot.
Crepidula is a commonly occurring gastropod on boat bottoms, pilings, and rocks, especially near harbors. The sculpture of the shell often takes the form of the substrate. This species ranges round the world. '