Read an Excerpt
THE CLASSES OF MOLLUSKS
All mollusks have soft bodies. The thin, fleshy mantle usually secretes a limy shell, either as a single cone or a pair of valves, or in 8 parts. Some mollusks lack a shell or are covered with hundreds of thin needlelike spines called spicules. More than half of all species are marine; the others live on land or in freshwater.
SNAILS, or gastropods, have a single shell, usually coiled. They have a distinct head with tentacles and a rasping tongue (the radula). Most of the more than 40,000 species have shells. See section starting here.
BIVALVES, or pelecypods, are mollusks with two valves joined by a hinge, a horny ligament, and one or two muscles. Most of the more than 10,000 species are marine; others are fresh water. See section startinghere.
CEPHALOPODS include squid, octopus and the Nautilus. Very active animals with large eyes, powerful jaws and with 8–90 tentacles. About 600 species. See section starting here.
TUSK SHELLS (about 600 species, all marine) live in curved, toothlike shells open at both ends. See here.
CHITONS are primitive marine mollusks with 8plated shells embedded in tough tissue. There are about 600 shallow-water species.
MONOPLACOPHORA, until recently known only from fossils. A rare deep-sea primitive group. The soft parts are segmented.
APLACOPHORA are small, primitive, wormlike mollusks covered with hundreds of long, thin spicules or scales rather than a shell. Most are small (¼ inch) and found in deep water.
MAJOR GROUPS OF MARINE SNAILS
From the primitive limpets and slit shells to the highly evolved cones and bubble shells, the marine snails show great diversity in shape and sculpture. Of the hundreds of families of gastropods, those pictured in this family key include the vast majority of better-known sea snails apt to be found in amateur collections.
MAJOR GROUPS OF MARINE BIVALVES
BIVALVES are less numerous than marine gastropods but are of greater economic value. Clams, oysters, mussels and scallops are eaten. One group produces nearly all natural and cultured pearls. The families shown on the tree are most commonly seen in collections.
OTHER MAJOR GROUPS OF SEASHELLS
CEPHALOPODS include the octopus, which has no shell, and the squids, with a thin internal shell. The Nautilus of the Indo-Pacific has a smooth, chambered shell. The Argonaut's paper-thin shell is an eggcase. See section starting here.
CHITONS are a group of flattened mollusks, some wormlike, most covered with eight shingle-like, overlapping plates held in place by a muscular ring called the girdle. Most live on rocks near shore and feed on algae.
TUSK SHELLS, or scaphopods, are tooth-shaped shells found in shallow and deep water. These odd mollusks lack gills (the mantle assumes this function), head, eyes or true tentacles. Some species were once highly valued by American Indians.
YOUR SHELL COLLECTION
A well-arranged, orderly collection of shells has many surprising rewards: a sense of scientific accomplishment, pride in building an educational and beautiful assortment, a stimulus to investigate an intriguing group of animals. Record locality data and best possible identification; follow a natural biological sequence, and your collection will serve as a useful guide and a constant source of satisfaction. Begin early to use a simple cabinet, multiple-sized paper trays, plastic boxes or match boxes, good labels, and a catalog with numbers corresponding to those written in India ink on the labels and specimens. Small shells, with numbered slips, may be put into glass vials, and the vials plugged with cotton.
A wooden cabinet (4 ft. high, 3 ft. deep and 2½ ft. wide) with wooden drawers on simple runners protects your shells from dust and careless hands.
Boxes made of cardboard of uniform height and of multiple sizes permit an orderly arrangement and best use of space.
Labels should bear the genus and species name. Most important are the locality data and other pertinent information.
COLLECTING MARINE SHELLS
Few mollusks live on the beach, but after storms fresh specimens may be cast upon the shore. Some appear only at certain seasons. Avoid damaged and water-worn shells.
Mollusks avoid bright sunlight. At low tide turn over rocks; dig in sand. Shore collecting at night in quiet bays is very profitable. Two people working together are most effective.
Going down where many shells live brings rich rewards in perfect specimens. Watch for trails in the sand. Put shells in a fine mesh bag. Follow safety rules.
A simple wire-mesh dredge, 24" wide, 36" long and 8" high, can be pulled by rope at depths down to 100 feet. Wash sand away and pick out shells.
Trade with collectors in foreign lands. Send perfect specimens with locality data. Wrap securely. A good way to increase your collection and to make friends. Be as generous as possible.
Many reliable dealers sell specimen shells. Compare prices from several mail listings and then use good judgment. Insist on locality data. Avoid acid-treated shells.
PREPARING SHELLS FOR STUDY
When collecting, observe the live animals and note their habits. So little is known about many species that every accurate observation is of value. Note color and other details, relative abundance, type of bottom, food, egg-laying or mating habits, methods of concealment, water temperature, associated plants and animals. Record your facts in a field notebook and note or photograph their habits. When cataloging, enter the notebook page on the collection label.
The soft parts and shells of mollusks may be permanently preserved in 70% alcohol. If not to be used for anatomical study, clams and snails may be boiled in water for five minutes and the "meat" removed with a bent pin or ice pick. Save the operculum, or trapdoor, to each snail. It is unwise to use acid on shells. Clean exterior with fine wire brush or buffing wheel.
Be considerate of nature and other collectors when looking for live shells. Disturb the habitat as little as possible, and turn back rocks as you found them. Otherwise, the eggs, young and food of snails will be killed by direct sunlight. Pollution and upsetting the ecology of the ocean shores are the main reasons for the reduction of live shells, but collectors can help by taking only a few of each kind. Leave young or poor specimens, since they will grow to lay more eggs and produce additional generations. In some states shellfishery laws prohibit the collecting of various kinds at special seasons or under certain sizes. Find out about the pertinent laws and regulations in your area, and follow them.
Basic information about malacology, the study of mollusks, or conchology, the study of mollusks and shells, can be found in the books listed below. You can also learn much from visits to natural history museums and aquariums. Curators of these collections can give professional advice. Check the Internet for Web sites of local, national, and international organizations.
THE WORLD OF MARINE SHELLS
Although the seas, which cover 72 percent of the earth's surface, are interconnected, parts of the oceans are isolated by land masses. Ocean currents, water temperatures and differences in salinity also act as barriers and create smaller sub-areas within faunistic provinces. Present faunistic boundaries were largely determined during the Pliocene, 9 million years ago. These are not clearly defined; some species invade the waters of neighboring provinces. Temperature is an important isolating factor. Within a province there may be special habitats suitable only to certain species — coral reefs, muddy or sandy bottoms, mangrove swamps or rocky shores. Some groups flourish in certain provinces, such as the limpets in South Africa and the cowries in the Indo-Pacific. Some mollusks are associated only with certain other animals, such as the wentletraps with sea anemones, and rapa snails with soft corals.
DISTRIBUTION OF MOLLUSKS WITH DEPTH
THE PELAGIC WORLD
Adults of several hundred species of mollusks live near the surface of the ocean. Some float, some are attached to sargassum weed, others hover in mid-water.
THE LITTORAL WORLD
A million miles of the world's intertidal shoreline support a rich fauna of periwinkles, limpets, burrowing clams, mussels and other species living between high- and low-tide level.
THE SHALLOW-WATER WORLD
Most of the marine mollusks live on the continental shelves and in coral reefs from the low-tide line to depths of about 400 feet. The relatively quiet waters and growth of algae permit a rich fauna to exist.
THE ABYSSAL WORLD
Small, mainly colorless shells live in the lightless depths of the ocean where temperatures are near freezing. Abyssal species are somewhat similar in all parts of the world. Squids have phosphorescent lights of blue, red and white.
Deep-sea mollusks living near the equator are found in much shallower waters in the polar seas where the water is cold. Some food comes from pelagic plants and animals which die and sink to the bottom. Both clams and snails have been found 3 miles down.
Stretching from Washington to parts of Baja California is a cool-water fauna of over 2,500 species. To the north is the cold-water Aleutian Province, some of whose species find their way as far south as northern California. In southern California, elements of the Panamic Province, a much warmer area, begin to appear. The California Province is rich in abalones, murex rock shells, limpets, and chitons. Among some of the characteristic species are the Kelp-weed Scallop and the Purple Dwarf Olive.
From the shores of the Carolinas, to the northern half of Florida and westward into Texas, the temperate-water Carolinian Province is characterized by Quahog Clams (Mercenaria) and by such species as the Shark-eye Moon Snail and the Marsh Periwinkle. The southern tip of Florida belongs to the tropical Caribbean Province. To the north, from Maine to Labrador, is the colder Boreal Province with a different and less rich shell fauna. The New England Neptune lives to the north.
The largest and richest shell region in the world extends from the shores of East Africa eastward through the East Indies to Polynesia. Notable for its abundance of colorful shells, it supports many strange and unique mollusks, such as the Giant Clams (Tridacna), the Scorpion Conchs (Lambis), and the Heart Cockles (Corculum). Most of the Indo-Pacific is characterized by tropical waters and coral reefs. The province is further divided into more or less isolated sub-regions.
THE RED SEA is an isolated, warm-water pocket of the Indian Ocean noted for its many peculiar subspecies and such unique species as the Lineated Conch (Strombusfasciatus Born), and Red-spotted Cowrie (Cypraea erythraeenis Sowerby).
AUSTRALIA is, along its tropical northern half, a land of rare and colorful volutes and strange Spiny Vase Shells (Tudicula). The seas are shallow with strong tides. The seas of southern Australia are much colder and have many different shells, such as the giant phasianellas.
THE HAWAIIAN CHAIN of volcanic islands in the central Pacific lacks many common Indo-Pacific species. It has some unique cowries and cone shells. The Tiger Cowrie, common elsewhere, is rare here and very large.
THE PHILIPPINES, consisting of thousands of islands, are very rich in mollusks. Several unique kinds are found in these waters, including the Imperial Volute and the Zambo Murex. Some normally uncommon species are abundant on the reefs of Philippine islands.
From the Gulf of California to northern Ecuador, the tropical Panamic Province supports a rich, colorful fauna of over 2,000 marine shells. Connected with the Caribbean until about 2 million years ago, the fauna resembles that of the West Indies. Tidal ranges are extreme in this area. The genus Strombina and such species as the Tent Olive are native.
Centered in the West Indies, this tropical province extends north to southern Florida and Bermuda. Many Caribbean elements spread out to the south as far as Brazil. Among the characteristic species are the Pink Conch, the Wide-mouthed Purpura and the Sunrise Tellin. The fauna is rich in Cassis, Murex and Tellina. The larger West Indian islands have over 1,200 species of shelled marine mollusks. Isolated coral islands, poor in food, have much less diverse mollusk faunas.
The most isolated of the world's major seas, the Mediterranean is relatively shallow and less dense than the Atlantic. Its fauna of 1,400 species of mollusks spreads around Portugal to southern France and along the northwest coast of Africa. Also known as the Lusitanian Province, it contains such unique shells as the Pelican's Foot, Jacob's Scallop, and the Murex Dye Shells.
Lying between the cold-water Aleutian Province and the tropical Indo-Pacific, the central islands of Japan contain a rich and distinct temperate marine fauna.
SOUTH AFRICAN PROVINCE
Cool, rough seas pound the rocky shoreline of South Africa. Its isolated fauna of about 900 species is rich in giant limpets, turbans and Thais rocky shells, plus strange, cool-water cowries and cone shells.
GASTROPODS, or univalves, single-shelled mollusks, include snails, conchs, periwinkles and whelks. More than half of the over 70,000 species are marine; the remainder are terrestrial and fresh-water. The fleshy, cape-like mantle produces a hard shell, while the foot may produce a horny operculum. Feeding is aided by a special set of teeth known as the radula. The sexes are separate in many marine species. Eggs are laid into the water or in capsules. A free-swimming larva, or "veliger," emerges which grows into a shelled adult. Most gastropods live 5 to 6 years; some may survive 20 or 30. Univalves may be carnivorous, herbivorous or even parasitic.
SLIT SHELLS (Pleurotomariidae) are primitive snails characterized by paired gills and kidneys. The slit in the shell is a natural opening for the passage of water and waste materials. The slit snails, found in very early fossil deposits, were once considered to be extinct. Today, 25 living deep-water species are known.
The operculum of the slit shells is thin, corneous, and brown and has many whorls.
This relatively small operculum is attached to the foot.
ABALONE shells (Haliotidae), shown on this and the next page, resemble a valve of a large clam, except for the spiral whorl. The animal has a large, flat and muscular foot by which it holds fast to rocks. Sea water is drawn in under the edges of the shell; it passes over the gills, and leaves through the natural holes. The foot is edible and highly esteemed. The iridescent shell is used in costume jewelry. Over a hundred species are known. They are vegetarians.
Excerpted from "Seashells of the World"
Copyright © 2002 St. Martin's Press.
Excerpted by permission of St. Martin's Press.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.