For 10 points, name this phylum, members of which have a mantle that is responsible for secreting the shell, and include chitons, clams, oysters, snails, and squids.
The first host of an endoparasitic digenea and the intermediate host of species of Schistosoma are members of this phylum. Mercenaria mercenaria is a member of this phylum that contains a pallial line, a ctenidium composed of demibranchs, byssal glands, a ventricle wrapped around the rectum, a protuberance known as the umbo, and a chitinous toothed structure called the radula. Eric Kandel uses the ganglia of one member of this phylum for neurophysiological studies. In addition to the model organism Aplysia, this phylum consists of members in classes such as Polyplacophora, Bivalvia, and Cephalopoda. For 10 points, name this phylum, members of which have a mantle that is responsible for secreting the shell, and include chitons, clams, oysters, snails, and squids.
The first host of an endoparasitic digenea and the intermediate host of species of Schistosoma are members of this phylum.
 mollusca [or molluscs]