ShellThe hard cover over the back. The mantle lays it down and strengthens it with calcium carbonate.
MantleThe sheet of body wall that covers the back. It makes the shell, and at the rear it hangs down to roof over the mantle cavity.
FootThe broad muscular underside. Different mollusks use it for creeping, for holding on to a rock or for burrowing.
HeadThe front end of the animal, which carries the mouth.
MouthThe opening at the front of the head, where food goes in.
Inside 7
RadulaA ribbon of tiny teeth inside the mouth. It is used to rasp food off a surface. Snails and squid have one. Clams and mussels do not.
Visceral massThe hump of soft organs above the foot. These are the gut, the heart, the kidneys and the rest.
StomachThe widest part of the gut. Food comes to it from the mouth, and the intestine leads on from it to the anus.
HeartA small pump high in the visceral mass, in its own space. It pushes blood out among the organs.
Mantle cavityThe space under the mantle at the rear. Water flows through it over the gills, and the anus and the kidneys empty into it.
GillsTake oxygen from the water flowing through the mantle cavity. Comb-shaped gills, called ctenidia.
AnusThe end of the gut. It opens into the mantle cavity, so the water leaving carries the waste away.
How this list was compiled: Every name checked on 2026-09-30 in two sources. Wikipedia, Mollusca, Radula, Mantle and Ctenidium, https://en.wikipedia.org/wiki/Mollusca. University of California Museum of Paleontology, The Mollusca, https://ucmp.berkeley.edu/taxa/inverts/mollusca/mollusca.php. R. W. Hegner, College Zoology (1912, public domain), https://archive.org/details/collegezoology00hegn. H. S. Pratt, A Course in Invertebrate Zoology (1902, public domain), https://archive.org/details/courseininverteb00prat. Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work
How it works
The parts of a mollusc are the same in a snail, a clam and a squid, though each has changed them. This drawing is a made-up simple mollusk, cut lengthwise, of the kind zoology books use to show that shared plan.
Read the full guide
Outside
The shell covers the back, and the mantle under it makes the shell. The head is at the front with the mouth. The foot is the broad muscular sole. These are the parts of a mollusk that show from outside.
Inside
The visceral mass holds the organs: the stomach, the rest of the gut and the heart. Inside the mouth is the radula, a ribbon of teeth. At the rear the mantle roofs over the mantle cavity, where the gills hang and the anus opens. Press Quiz me to name each part yourself.
Mollusc and mollusk are the same word: mollusk is the usual American spelling, mollusc the British one.
Questions and answers
What body parts do all mollusks have?
A mantle, which usually makes a shell, a mantle cavity, a muscular foot and a visceral mass holding the organs. Most also have a radula, but bivalves such as clams and mussels have lost it.
What does the mantle do?
It covers the back of the animal and lays down the shell. At the rear it hangs over the mantle cavity, the space that holds the gills.
What is a radula?
A ribbon of tiny teeth inside the mouth. A snail uses it to rasp food off a surface. Clams, mussels and other bivalves have none.
Is this a real animal?
No. It is a plan that zoology books draw to show what mollusks share. A real snail, clam or squid has each of these parts in a changed form.