- A muscular foot. It is usually used as an organ of locomotion, like gastropods, but bivalves use it to dig or cephalopods to propel themselves.
- Head, with mouth and sense organs, in which the radula stands out, a feeding organ formed by rows of curved chitin teeth that allow them to scrape food. It is something similar to a language but with a more complex function.
- Mantle that surrounds the internal organs that sometimes secretes a calcareous shell that serves as support and protection for the mollusk.
Most molluscs have an internal or external calcareous shell that serves as an exoskeleton, protecting and supporting the animal. If they have an external shell, it may be made up of one or two valves. Other species, such as octopuses and slugs, do not have a shell.
Mollusks have a complete digestive tube.
Mollusc respiration is cutaneous (through the skin) or through gills.
They reproduce sexually, they are oviparous.
The main classes of molluscs are: