Distribution: Massachusetts to Florida, Texas; West Indies; Bermuda. Size: 6 to 12 mm Description: External color varies from tan to purple with reddish lines distinct on tan shells, with some shells having brown spots or maculations on a white base, interior of shell chestnut brown to bluish-brown; shape limpetlike; outer sculpture smooth with fine radial growth lines; inner portion of shell with a septum (deck) that covers less than half the aperture and is slightly longer on left than on right, midline almost straight, muscle scar located on right side just beneath right corner of the deck; apex centrally located, near posterior margin; aperture large, oval with thin margin.
Habitat: Intertidally on shell, rocks, and grass to moderate depths. Depth range 0 to 70 m (230 ft).
Remarks: These snails are regularly found living on Argopecten irradians amplicostatus (Dall, 1898). See Andrews (1977); Hoagland (1977).