Argonaut, Argonauta argo

This shell is also called the Paper Nautilus, but the animal that makes it is actually an octopus that lives in the open ocean. The shell is only made by females, and its function is to protect the animal’s eggs until they hatch. The light but surprisingly rigid shells are sometimes cast up on beaches after storms, and can be found in almost all parts of the world. There are several species, of which Argonauta argo is the largest.