Petaloconchus keenae Hadfield and Kay, 1972. Shell: of medium size (diameter of whorls up to 10 mm; apertural diameter, 5 mm); early whorls of teleoconch forming a conical coil on the substratum, later whorls emergent and projecting several centimeters above the substratum. Aperture circular. Sculpture of axial ribs crossed by obsolete striae. Cream, red-brown, or dark purple, with newly deposited shell of older individual pale lavender. Operculum: slightly concave, with a thickened and raised black center and a small mamilla on the pedal surface; chitinous, thin and transparent; about one-third the diameter of the aperture. Animal: head, foot, tentacles and mantle handsomely pigmented dark purple to rosy brown, sprinkled with white dots and with yellow on the rolled edges of the mantle. Mantle margin split in the females.
This is the most common and ubiquitous vermetid in the Hawaiian Islands, occurring intertidally and subtidally wherever there is suitable substrate. It is the dominant species on coralline algal-covered surfaces of patch reefs in Kaneohe Bay, Oahu, and forms fingerlike protuberances in coral in subtidal coral communities.
P. keenae was described from the Hawaiian Islands, and also occurs in the Marshall Islands.