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.