This etext was produced by Justin (dopefish_justin@yahoo.com).
Millions of people throughout the world have found many hoursof pleasure, adventure and education by collecting either rocksor shells.
This booklet won't tell you everything there is to know aboutrocks and shells. That would require many large volumes. We onlywant to arouse your curiosity about two delightful pastimes thatare so broad and varied that they can lead to a career or asatisfying hobby.
Shell Oil Company's interest in the subjects comes from itshistory and the nature of its business. The name—chosen by acompany that was founded years before anyone thought of drillingfor oil—comes from the seashells this company brought from theOrient for use in mother-of-pearl items such as buttons and knifehandles.
Now its world-famous emblem (the Pecten) is recognized by millionsof people in every walk of life. It's on service stations, trucks,buildings, oil derricks and chemical plants. Even the company'sindustrial lubricants are named for shells because shells havethe same scientific names everywhere in the world.
For an oil company, rocks have a special interest. Crude oil isfound not in underground lakes or pools but in the tiny spacesbetween grains of sand or in the pores of rocks. Only certaintypes of rock formations are favorable to the accumulation of oil.Thus, oilmen need to know everything they can about the right kindof rocks.
Shell has scientists who work with rocks all day and laboratoriesfilled with rock, mineral and crystal specimens. We are alwayslearning new things about them.
The pages that follow provide basic information about two subjectsthat can be richly rewarding whether you follow them for profit,as Shell does, or for pleasure, as millions of people around theworld do.
First, a seashell is one of the 100,000 species of backbonelessanimals 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 andsea urchins.
True molluscan shells come in two main varieties: BIVALVES andUNIVALVES. Bivalves have two valves, fitting together along atoothed hinge on one side, and kept closed by means of ADDUCTORMUSCLES. Univalves have only one shell, usually coiled, butsometimes shaped like a cap or miniature volcano. Some marineunivalves can seal themselves inside with an operculum, whichcovers the open end of the shell like a trap door. Although shellstake on many different shapes, they are much alike inside. Eachhas a foot, a breathing siphon, a tiny brain and heart, and afleshy mantle which secretes lime for shell-building. Most truemollusks have eyes, but a few are blind. Many have teeth, calledRADULAE.
Like any other animal, the mollusk generally moves about. Itpushes along on the ocean floor on its foot, or it might swim alittle. It lays millions of eggs and hatches countless babymollusks. It lives its life in its shell, lugging it around,snuggling into it when alarmed, burr