THE MOON SHELLS AND VELVET SHELLS - FAMILY NATICIDAE Shell globular or ear-shaped, with wide aperture; foot very large, prolonged in front and behind; radula large; mantle often engulfing the shell. Predatory mollusks which burrow in the sand for bivalves.
Genus NATICA, Lam. (LUNATIA, Gray) Shell oval, globular, solid, porcellanous, smooth, with transparent epidermis, umbilicated; operculum large, semi lunar; foot broad in front, furnished with an upper fold that is reflected back over the head and front margin of the shell. Eggs laid in collar-shaped band covered with sand. Active, carni vorous mollusks, living in temperate and warm seas.
The Moon Shell (N. heros, Say), round and smooth as an apple, is a familiar object on our east coast. The spire is flattened and very small, the coils few; the last whorl, very much larger than the others, ends in an ear-shaped aperture. The large umbilicus extends to the apex, which is often worn off, letting water pass through. The colour of these shells is ashen, streaked or clouded with brown inside and out. Dead shells are soon wave-worn and disintegrated; the protective epidermis goes with their lost youth. The operculum is horny and spiral, the nucleus near one edge.
No adornment is to be seen upon the strong house that shelters this businesslike mollusk butcher. He rolls up his sleeves, so to speak, and goes after his prey in dead earnest. Put one in a tank of sea water, with sand in the bottom, and before long he recovers his equanimity, and unlocks his door. The amount of foot he unfolds is a matter of amazement when the size of the shell is taken into account. A flattened pad of flesh three times as long as the shell's diameter, and half as wide as long—this is 143 The Moon Shells and Velvet Shells the burrowing, gliding organ of locomotion. In shape it is some what like the bottom of an old-fashioned flatiron; the broad, truncated end is forward. A fleshy band on top of the foot folds back over the head, protecting it as the burrowing foot drags the body rapidly after it through the wet sand. The eyes
are wanting or buried under a thick epidermis.
This blind, mole-like mollusk finds plenty to eat in the zone just under the surface of the sand. Clams and other shell fish are there. Down comes the hood from over the head when a victim is met. The long proboscis is set, and the radula it con tains soon has a neat round hole drilled in the shell, through which the soft parts are extracted by the sucking mouth of the bloodthirsty Natica.
The largest holes drilled in various bivalve shells are usually charged to the Naticas, although the evidence is partly circum stantial. The activity of the mollusk argues a keen appetite, and its predatory reputation is quite lived up to if a single speci men is put into an aquarium with clams and a variety of other mollusks of less strenuous habits. Well may Natica be bold, for at the least warning of danger it draws in the foot, and the horny operculum locks the door tight.
The eggs are laid in a sticky mass of clear jelly which is moulded over the shell; this explains its peculiar collar shape. There is but one layer of egg cases, arranged in regular quincunx order. A layer of fine sand covers each side of the collar, making it about the thickness of an orange peel. While this remains in the water the mucus is rubber-like, and the eggs are safely con cealed under the protective film of gray sand. Cast ashore the sand collar becomes dry and brittle. Who has not seen these collars, six inches in diameter and open at one side, lying on the beach? It is useless to try to carry one home without having it shattered. Near hatching time the sand falls off, and the eggs become visible, N. heros ranges along shore in sand or mud, devouring, besides living bivalves, dead fish and other victims of accident. On New Jersey beaches the surf clam (Mactra solidissima) seems to be the prey it prefers. Its method is to clasp the victim in its voluminous foot while the drill attacks the shell near the hinge. Diameter, 3 to 41 inches.