They have a strong inner shell layer composed of nacre, also known as mother of pearl.

The middle shell layer is organic, and is also the thickest of the three (about 150 μm).

Clear coats traditionally provide an extra shell layer of protection from the following:

This shell layer is composed of a type of protein known as conchiolin.

These fertilized eggs, termed winter eggs, are provided with an extra shell layer called the ephippium.

In no case would this iridescence have been visible during the animal's life; additional shell layers covered it.

The outermost clothes are called the shell layer, but only if they block wind or water, or have good mechanical strength.

For example, when one is jogging, no traditional shell layer is likely to be able to transfer enough moisture to keep the wearer feeling dry.

Removing the shell layer during heavy exercise can pose problems if the clothes underneath lack required mechanical strength or water proofing.

They have nacre as the inner shell layer.