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FISSURELLIDAE 99
ately larger apical hole which is sharp at its top edge and which is nearer the
center of the shell. The ends of the shell are slightly turned up and the sides
are slightly concave. Sculpture of about 2 dozen heavily scaled, radial ribs
and numerous, fine, thread-like concentric ridges. Color whitish with weak
mauve or brown discoloring. Commonly dredged off southeastern Florida,
from 6 to 60 fathoms.
Lucapinella callomarginata Dall Hard-Edged Fleshy Limpet
Bodega Bay, California, to Nicaragua.
Plate i8e
% to I inch in length, narrower at the anterior end, quite flat. Base flat
and usually with strong crenulations on the under edge. Sides slightly con-
cave. Apical hole narrowly elongate, slightly nearer the anterior end, about
Vb the length of the shell and with flat inner sides. Sculpture coarsely cancel-
late with the radial ribs stronger and often scaled. Color dark-gray with
irregular, darker, radial color-rays. Rather rare under rocks in the low tide
zone.
Genus Megathura Pilsbry 1890
Megathiira cremilata Sowerby Great Keyhole Limpet
Monterey, California, to Cedros Island, Mexico.
Plate 1 8a
2% to 4 inches in length, Vo as high. Apical hole large, with rounded
sides, % the length of the shell, and bordered externally by a white margin.
Interior glossy-white. Basal edge finely crenulate. Exterior finely beaded
and light mauve-brown. Animal much larger than the shell, with a massive,
yellow foot and a black or brown mantle that nearly covers the entire shell.
Common in many low-tide, rocky areas, such as breakwaters.
Genus Megatebennus Pilsbry 1890
Megatebennus bimaculatus Dall Two-Spotted Keyhole Limpet
Alaska to Tres Marias Islands, Mexico.
Plate i8d
% to % inch in length, low, with ends turned slightly up. Apical hole
elongate-oval, located at the center of the shell and about % the length of
the shell. Numerous radial and concentric threads give a fine cancellate sculp-
turing. Color dark-gray to light-brown with a wide, darker ray on each side
of the hole, and occasionally at each end. Interior white to grayish. Animal
several times as large as the shell, variable in color—red, yellow or white.
Common under stones at low tide.