Mokoli'i Islet, Oahu, 3 feet, 21 mm

Uncommon under rocks in shallow water where it preys upon bivalves.  White with curved axial ribs crossed by closely-spaced spiral cords, aperture wine, usually eroded and encrusted with coralline algae.  Attains 0.8 inch, 22 mm.  Endemic to Hawaii.  Formerly known as Morula dumosa or Spinidrupa dumosa.