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is abundant and varied, some of the most colorful mollusks can be found. Coloring in shells probably has little to do with warn- ing or camouflage, the shell itself being pro- tection enough in most cases. The brilliant colors of some shells are a surprise to some people who may only be familiar with the worn and faded specimens found on a beach. It is only the living mollusk that will show its true colors. Classifying Shells To the casual observer of shells, there are two main types: the gastropods, or those that live in a single shell, such as a whelk; and the bivalves, or those that live in a pair of hinged shells, such as a clam. There are in

breed and pass on those features to the next generation. The murex shell, for example, has many long, pointed projections that are dec- orative to our eyes, and may appear to make the shell more cumbersome when moving along the seabed, but to a hungry fish they will represent a tough challenge. Trying to break open a shell with such armor is almost impossible, so the murex is usually left alone and a less well-armored species will be chosen as food. Some shells clearly appear to be made of calcium carbonate, due to their chalky appearance, but many are richly colored and patterned. Some of the coloring is due to the pigments available in the mollusk’s diet; in the warmer regions of the world, where food

The unusual uncoiled shell of Miller’s nutmeg, Trigonostoma mil- leri, is rare among the gastropod mol- lusks. This species lives in deep water off the coasts of Mexico and Galapagos, where it seems to prefer muddy seabeds.

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