Glossary

carnivore - eats meat
circumpharyngeal nerve ring - A ring of nerves and ganglia (the brain) that form a circular structure surrounding the pharynx.
coelom - cavity
ctenidia (singular: ctenidium) - Molluscan gills used in respiration and/or feeding. Many mollusks have a unique feature known as a bipectinate ctenidium supported by a cartilaginous rod. In other mollusks, this gill has been reduced or lost, or replaced by a secondary gill, which is not a true ctenidium.

herbivore - eats plant matter
hemocoel circulation - The hemocoel is a coelom (cavity) surrounding the heart. Mollusks do not have a system of arteries, veins and capillaries. When the blood is pumped out of the heart it passes into sinuses that carry it to the various organs. The blood collects in other sinuses and is then returned to the heart.

protostomal development - Those animals whose protostome (the invagination in larval development that forms during gastrulation) becomes the oral orifice (as opposed the deuterostomes, in which the invagination becomes the anus).

radula - (plural: radulae) A rasp-like structure in the mouth with numerous chitinous teeth used to scrape, pierce, tear, or cut off small pieces of food that are then directed into the digestive tract. In most mollusks, the radula is like a flexible file or a ribbon of teeth. Radulae are unique to mollusks; no other creatures have them. Bivalves and some gastropod species lack radulae; these absences are interpreted as evolutionary loss of the radula. Different species of mollusks often have differently shaped radulae, so examining the radulae can help identify species and resolve their relationships to each other. Some radulae, as in the cone snails, are modified into hypodermic darts to inject poison into the prey.

schizocoel coelomic cavities - A coelom is a cavity formed by a splitting of the embryonic mesoderm (connective tissue). As development progresses, this coelom becomes reduced to just cavities surrounding heart, kidneys, and gonads.
spicules

trochophore larva - The trochophore larva is generally globular, shaped like a toy top, with an equatorial band of cilia and an apical group of cilia. The trochophore larva is found in the life history of several phyla of animals including annelids, mollusks, and sipunculids. Because these three groups share the same larval type, they probably share a common ancestor.