I find this question somewhat ambiguous as it doesn't mention any particular story. However, if you want to know if trilobites pertains to the Appalachian Mountains, I can answer that.

Trilobites are the fossils of hard-shelled arthropods that supposedly lived in the seas during the Paleozoic Era of prehistoric Earth(approximately 520 million years ago). Paleontologists generally consider them to be one of the first complex life forms on the planet, and one of the most versatile. Wherever they are found gives evidence of the existence of ancient seas.

One such area of the United States where trilobites fossils are found is the Appalachian Mountain region of the southern states of Alabama, Georgia, South Carolina, North Carolina, Tennessee, Virginia, and Kentucky. They suggest this area was under water at some point in time.

Because there are several species of trilobite with each subspecies indigenous to a particular area of the globe, they can often be used in criminal forensics to pinpoint the approximate location of a crime or unusual event.