The formation of shells can create patterns. As the animal grows inside the shell, its home must get bigger, and so they grow their shells layer upon layer, creating 'growth-bands or growth increments, within the shell.

Stock photo: The formation of shells can create patterns. As the animal grows inside the shell, its home must get bigger, and so they grow their shells layer upon layer, creating 'growth-bands or growth increments, within the shell. was taken by simmons48 .