Simplify the following text for a Grade 10 native English-speaking person.
Original: Selection quickly acted on the resultant conical shells to form them to overlap into protective armor ; their original cones are homologous to the tips of the plates of modern chitons .
Simplified: Selection acted on the resultant conical shells to form them to overlap into protective armor . Their original cones are homologous with the tips of the plates of modern chitons .