👉 Ctenostomata is a genus of marine crustaceans in the class Mollusca. These animals are known for their hard shells, which can be up to 10 inches long and 4 inches wide. They have a tough shell that is composed of a soft, waxy substance called the "shell matrix" that provides protection from predators. Ctenostomata are typically found in coastal waters, such as the Pacific Ocean or the Atlantic Ocean. They are known for