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
This mollusk diagram quiz names a part and you tap it on the drawing. The animal is the simple mollusk that zoology books draw to show the plan a snail, a clam and a squid share, head to the left.
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Pairs that get mixed up
The shell is the arched cap on top; the mantle is the band of skin just under it. The mouth opens at the front of the head, and the anus is the end of the gut at the rear. The stomach is the bag in the middle of the hump, and the heart is the smaller organ high at its rear.
One mass and one space
The visceral mass is the whole hump of soft organs above the foot, not a single organ. The mantle cavity is the open space at the rear, under the hanging edge of the mantle, and the gills are the comb inside it.
A textbook may print ctenidia for the gills and pallium for the mantle. They are the same two parts.
Questions and answers
What parts are on the mollusk diagram quiz?
Twelve: five on the outside, then seven inside. A tentacle and an eye are drawn on the head but never asked, and the kidneys and the nerve cords are left off.
What are the main parts of a mollusk's body?
A head, a foot and a visceral mass, all covered by the mantle. The visceral mass is the soft part that holds the organs, so the stomach and the heart of this quiz both lie inside it.
What is the mantle cavity used for?
Breathing and excretion. The gills hang in it, and the gut and the kidneys empty into it, which is why the anus is found at the rear of the drawing, in the same space as the gills.
Do all mollusks have a shell?
No. The mantle usually lays down a shell, but some groups, such as the nudibranchs, have lost it. The drawing has the single cap-shaped shell that textbooks give their simple mollusk.