11⁄4 inch in maximum diameter, elliptical in outline, generally with a low apex which is placed 1⁄3 back from the front end. The 15 to 25 strong, coarse radiating ribs give the edge of the shell a strong crenulation. Color dirty gray-green. Underside of shell whitish, irregularly stained in the center with blackish brown. Edge of shell between the serrations is stained blackish to purplish brown. A common species found clinging to rocks high above the water line but within reach of the ocean spray. A. spectrum Nuttall is the same species. Do not confuse with the smaller A. conus which is evenly glossed, instead of coarse and dull, on its interior center.
Alaska to Oregon (common) to Lower California (rare).
1 to 2 inches in maximum diameter, almost round in outline, quite flat, with the apex toward the center of the shell. Smoothish, except for very fine radial riblets in young specimens. External color greenish gray with slate-gray radial bands or mottlings. Interior bluish white with faint or darkish brown spot. Inner edge with band of alternating bars of black or brown and bluish white. The name of this species was also known as tessulata Muller. The typical testudinalis from the Arctic Seas and New England rarely, if ever, exceeds a size of 11⁄2 inches, is not so round, and has a darker, more concentrated brown patch on the inside. Intergrades exist in Alaskan waters. The Pacific race was also named patina Esch.
Alaska to Mexico, clinging to the gastropod, Tegula.
1⁄4 inch in maximum diameter, high-conic, elliptical in outline, and solid black inside and out. In the northern part of its range, the Black Limpet is found living attached to the common snail, Tegula funebralis A. Adams.
Southern California to Gulf of California.
1⁄4 inch in maximum diameter, oblong in outline, side view distinctly triangular. Color whitish with 3 or 4 vertical, rather broad, brown stripes on each side. Found among coralline algae from the shore line down to several fathoms. Uncommon.
Santa Barbara, California, to Lower California.
