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 



Plate i8e 



Bodega Bay, California, to Nicaragua. 



% 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 



Plate 1 8a 



Monterey, California, to Cedros Island, Mexico. 



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 



Plate i8d 



Alaska to Tres Marias Islands, Mexico. 



% 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. 



