Archimedes (bryozoan) is an extinct animal that lived from the Carboniferous to the Permian Period. Archimedes had a spiral wall that wrapped around a corkscrew stalk that was anchored to the sea floor. The wall was covered in zooids, like all bryozoans.
Archimedes is named after the Archimedes Screw, because of the corkscrew stalk. Most fossils of Archimedes do not preserve the spiral wall. Instead they only preserve the unusual stalk.
Archimedes is unique because of its spiral shape. It is a kind of animal called a bryozoan, which means "moss animal." They are also commonly called "moss animals," and they are still alive today. But Archimedes has been extinct since the Permian.
These fossils of Archimedes only preserves the corkscrew stalk. The rest of it is usually not preserved because it is very brittle, like all bryozoans.