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CONTENTS
COLLECTING SEASHELLS
SEASHELLS. . .WHAT ARE THEY?
THE SHELL AS AN ARCHITECT
LET'S MEET SOME SHELLS
WHERE TO LOOK
STARTING A COLLECTION. . .HERE'S HOW
COLLECTING ROCKS
ROCKS ARE MADE OF MINERALS
MAIN KINDS OF ROCKS
COLLECTING
GEMS FOR THE LUCKY FEW
INTRODUCTION
Millions of people throughout the world have found many hours
of pleasure, adventure and education by collecting either rocks
or shells.
This booklet won't tell you everything there is to know about
rocks and shells. That would require many large volumes. We only
want to arouse your curiosity about two delightful pastimes that
are so broad and varied that they can lead to a career or a
satisfying hobby.
Shell Oil Company's interest in the subjects comes from its
history and the nature of its business. The name--chosen by a
company that was founded years before anyone thought of drilling
for oil--comes from the seashells this company brought from the
Orient for use in mother-of-pearl items such as buttons and knife
handles.
Now its world-famous emblem (the Pecten) is recognized by millions
of people in every walk of life. It's on service stations, trucks,
buildings, oil derricks and chemical plants. Even the company's
industrial lubricants are named for shells because shells have
the same scientific names everywhere in the world.
For an oil company, rocks have a special interest. Crude oil is
found not in underground lakes or pools but in the tiny spaces
between grains of sand or in the pores of rocks. Only certain
types of rock formations are favorable to the accumulation of oil.
Thus, oilmen need to know everything they can about the right kind
of rocks.
Shell has scientists who work with rocks all day and laboratories
filled with rock, mineral and crystal specimens. We are always
learning new things about them.
The pages that follow provide basic information about two subjects
that can be richly rewarding whether you follow them for profit,
as Shell does, or for pleasure, as millions of people around the
world do.
SEASHELLS. . .WHAT ARE THEY?
First, a seashell is one of the 100,000 species of backboneless
animals belonging to the zoological group known as the Mollusca.
Mollusks include not only the familiar clams, scallops and snails,
but also the squids, octopus and Chambered Nautilus. Other "shells"
found in the ocean include those of crabs, lobsters, barnacles and
sea urchins.
True molluscan shells come in two main varieties: BIVALVES and
UNIVALVES. Bivalves have two valves, fitting together along a
toothed hinge on one side, and kept closed by means of ADDUCTOR
MUSCLES. Univalves have only one shell, usually coiled, but
sometimes shaped like a cap or miniature volcano. Some marine
univalves can seal themselves inside with an operculum, which
covers the open end of the shell like a trap door. Although shells
take on many different shapes, they are much alike inside. Each
has a foot, a breathing siphon, a tiny brain and heart, and a
fleshy mantle which secretes lime for shell-building. Most true
mollusks have eyes, but a few are blind. Many have teeth, called
RADULAE.
Like any other animal, the mollusk generally moves about. It
pushes along on the ocean floor on its foot, or it might swim a
little. It lays millions of eggs and hatches countless baby
mollusks. It lives its life in its shell, lugging it around,
snuggling into it when alarmed, burrowing into mud, fastening
itself to a rock and creating ingenious camouflage. It builds its
calcareous house with a great instinctive talent for color and
sculpture. . .and the closer it lives to the tropical zones, the
more beautifully spectacular is its art.
The two parts of a bivalve shell are like thin saucers, concave
inside, convex outside. The inside is smooth, polished. The outside
is rougher, sometimes with graceful ribs or concentric ridges or
combinations of both. Univalves are conical and spiraling, with
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