THE COCKLES. HEART SHELLS FAMILY CARDIIDAE. Shell regularly equivalve, heart-shaped, radiately ribbed; sculpture of posterior area different from front and sides; hinge with one or two cardinal teeth and two laterals on each valve; ligament short, external; muscle scars squarish; pallial line sinuous behind; mantle open in front; ocelli on border; siphons short, fringed at tip; gills two on each side, thick, joined posteriorly; foot large, sickle-shaped, without byssus.
Free mollusks, marine or in brackish water.
Genus CARDIUM, Linn.
Shell globose, heart-shaped when viewed endwise; beaks prominent, nearly central; ribs strong; margins of valves crenu lated. A large genus, one hundred species, of world-wide dis tribution, near low water, in sand or mud, forming extensive beds in sheltered bays or estuaries.
The Common or Edible Cockle (C. edule, Linn.) needs no description in Europe. It is so extensively "raked in" for food and bait from the sandy and muddy shallows skirting the British Isles and the Continent as to be the most familiar bivalve in fishing villages and in the city fish markets.
The solid shells bear about twenty-five strong, rounded ribs, with nodules or squamate scales, if the creature lives in muddy water; if in sand, these trimmings are worn off by attrition, as the mollusk moves about freely. Thrusting out the long foot to its full extent, the cockle lifts itself with a quick, twisting motion and flops a distance of several inches. The tip of the foot dilates, forming a fulcrum upon which the muscles act in this awkward mode of locomotion.
The foot is white, the mantle yellow, fringed at the border. A red band near the edge trims the yellow surface of the shells.
357 The Cockles. Heart Shells All sorts of fancy articles, pincushions, purses, even shell flowers, are made of cockle shells. Length and width, 2 inches.
Habitat.— Europe.
The Spiny Cockle or Red Nose (C. aculeatum, Linn.) is a big, red mollusk in a spiny, broad-ribbed shell, yellow, tinged red. The bright red foot is long and pointed, which accounts for its name. Length and width, 3 inches.
Habitat.— Irish Channel.
The Giant Cockle (C. lima, Linn.) is as big as a cocoanut; the shell has a capacity of a quart or more. Its ventricose valves
are scored with wide, shallow ditches between low flat ridges, smooth and polished, and pink shading darker toward the margins.
Habitat.— East coast of Africa.
The Large Cockle (C. magnum, Born.) is ours, and few cock les or other bivalves in the world excel it in size and beauty. It is roomy, somewhat oblique, and flattened posteriorly. Its ribs are close, deep, and flat, crenulated on the anterior area. The yellowish brown surface is painted with scattered spots of dark or purplish brown. The posterior area is uniformly dark. Ribs 35. Diameter 3 to 5 inches.
Habitat.— Virginia to West Indies and Texas.
C. isocardia, Linn., is obliquely oval, with recurved spines set on its deeply chiselled ribs. The anterior area shows larger, more blunt tubercles. The lips of the shell meet in fine scallops. Outside, the shell is yellow, stained with purplish brown. Inside it is salmon pink shading to purple. Diameter, 3 to 4 inches.
Habitat.—Cape Hatteras to West Florida.
C. muricatum, Linn., has a circular outline, and thirty-six ribs, all sharply cusped. The spines of the middle dozen ribs are directed toward some distant object, in quite the opposite quar ter from the object at which all the other points have taken aim. This gives the species its chief distinction. The yellow-tinged surface is splotched with brown. The inner lip is orange. Diam eter, 1 to 21 inches.
Habitat.— North Carolina to West Indies.
The Iceland Cockle (C. I slandicum, Linn.) is obliquely roundish, thin, with thirty-six flat or spiny ribs, and a prominent, elevated hinge. A dark green or gray epidermis covers the pale shell. Length, 2 or 3 inches.
Habitat.— Arctic seas to Cipe Cod.
358 The Cockles. Heart Shells C. pinnulatum, Conr., is small, thin, orbicular, with rounded ribs, creamy white, flamed with brown. This is an abundant species, and a favourite food of fishes. Fine specimens may be obtained from their stomachs, to say nothing of the rarer species often discovered there. The mollusk is very active, scurrying over gravelly bottom at a surprising rate by means of its exten sible, recurved foot. Diameter, I inch.