THE CUP-AND-SAUCER LIMPETS Genus CRUCIBULUM, Schum.
Shell shield-shaped with funnel-shaped cup inside.
The Limpet (C. scutellatum, Gray) has a heavy, shield-shaped shell with strong radiating ribs crossed by concentric ridges. The hooked beak is near the centre. The general colour is brown. Inside the shell is of a darker colour and polished. The variation in form, height and markings has led to the erecting of a great many species which have been reduced more recently to the rank of varieties. Young shells differ markedly from adults. Length, 2-1 inches.
Habitat.—West coast of South America.
Var. auriculatum is a flat form, pale brown, usually mottled with very rough radiate ridges. It is the West Indian form.
Var. tubiferum extends north from Chili to California. Small, close ridges radiate from the apex, certain of them bearing sharp, hollow prickles.
The Limpet (C. striatum, Say) of our east coast is a small, pale cone with circular base and radiating ridges that form a scalloped border. The beak is hooked and almost overhangs the posterior edge of the shell. The flaring cup is attached by its side. Length, less than 1 inch.
Habitat.— Whole Atlantic coast.
Genus CALYPTRZEA, Lam.
Shell conical, with central spiral apex; aperture basal, circular; diaphragm spiral, margin twisted, free margin convex.
The European Limpet (C. Sinensis, Linn.) is well known. Its cone is regular, with a spiral apex and circular base. The cup takes a spiral turn or two, forming
a deep umbilicus. The shell is thin and smooth and round, pale yellow, shining inside. Quite often the pebble to which the young mollusk attaches itself is so small that the aperture of the shell reaches the outer limits of its surface before the adult size is 151 The Slipper Shells. Cup—and-saucer Limpets reached. Unable to grow further in this direction, the shell enlarges vertically, lifting the apex but keeping the base the same seize. This adaptability to environment produces great variation in form within the species.
The female lays her yellow eggs in flat capsules which are all attached to a common stalk as are the petals of a rose. Each capsule is transparent and contains about a dozen eggs. The shield-shaped shell protects the mother mollusk and her eggs. The young hatch and are kept between the foot and the stone to which the shell is attached until they acquire the neck frills of hairs by which they are equipped for a free-swimming life.
The Chinese Hat (C. mamillaris, Brod.) is a low, white cone with a central peak. It would require a doll mandarin to fit it. Inside is the characteristic twisted deck of the genus. The cir cular rim is inch in diameter.
Habitat.— California northward.