Var. limulata, Cpr., has a black band around the apex, and a black border inside the aperture. The rest of the interior 232 The Limpets. Tent Shells is olive green. A cap-shaped form, with coarse sculpturing is the extreme of variation in this species. Length, i 1 inches. Habitat.— California.
The Ghost Limpet (A. spectrum, Rve.) has a ghostly print of a human hand showing under the white callus that lines the shell. Outside, strong rough ridges run from the peak to the crenulated margin. They are whitish, with dots of brown filling in the depressions. Shell heavy. Length, 11 inches.
Habitat.— Sitka to Lower California.
The Mask Limpet (A. persona, Eschs.) has its beak bent forward until it is parallel with the base, and almost above the anterior edge of the shell. Behind the apex the curve is rounding. Thus the shell has almost a perfect mask form. Strong rounded ridges, with wide flat spaces between, radiate from apex to margin, crenulating the latter. The colouring varies from olive green to black, with speckles or stripes of white.
From San Francisco north and south the type diverges, becom ing more strongly ribbed behind the apex as we go north, and tend ing to smaller and narrower ribs and more spreading sides as we go south. It is an exceedingly variable species. Length, i inch.
Habitat.— Sitka to Lower California.
The Shield Limpet (A. pelta, Eschs.) has an oval, shield shaped shell, with pointed apex near the centre, and low, coarse ribs radiating from it. A narrow black band follows the edge of the lin ing, which is oftenest made up of scallops or disconnected square spots. The peak is more elevated than usual in a small form found near Olympia, living on the valves of mussels. The typical colour ing is gray, striped with black, often tesselated. Length, 2 inches.
Habitat.— Aleutian Islands to Southern California.
The White Cap (A. mitra, Eschs.) has a creamy smooth shell, rounded up to a decided peak. The dead shells are often picked up on Pacific beaches, but the mollusk is rarely seen alive. It is scarcely an inch in height, and slightly more than an inch across the almost circular base.