Final answer:
The mollusca class with 8 overlapping plates is the Polyplacophora, known as chitons, featuring an armor-like shell, a suction-capable foot, and a mantle with calcareous spines.
Step-by-step explanation:
The class of mollusca that has 8 overlapping plates is the class Polyplacophora, commonly known as chitons. These marine organisms are known for their characteristic armor-like shell composed of eight limy plates that provide protection. Chitons have a broad, ventral foot that is adapted for suctioning onto rocks and other substrates, and a mantle that extends beyond the edge of the shell. Not only do these plates offer protection, but the exposed mantle edge, often with calcareous spines, also helps ward off predators. Chitons breathe through multiple pairs of gills located in the mantle cavity. Their radula, with teeth made of ultra-hard magnetite, is uniquely adapted for scraping food off rocky surfaces in their marine environments.