Final answer:
The class Cephalopoda within the phylum Mollusca consists of several subclasses, including Nautiloidea, Coleoidea, and Ammonoidea. Nautiloidea includes nautilus, Coleoidea includes squids and octopuses, and Ammonoidea includes extinct ammonites.
Step-by-step explanation:
The class Cephalopoda within the phylum Mollusca consists of several subclasses. However, the number of subclasses within class Cephalopoda can vary depending on different classification systems and scientific research. In general, the commonly recognized subclasses within Cephalopoda include Nautiloidea, Coleoidea, and Ammonoidea. Nautiloidea includes creatures such as nautilus, Coleoidea includes squids and octopuses, and Ammonoidea includes extinct species of ammonites.