Many classify this shell as a member of the Nautilus family. It does not have chambers like the nautilus nor is there any similarity in the shell construction. The animal in the shell is a member of the octopus family. Because the shell is paper thin and resembles a Chambered Nautilus shell on the outside it has become known as the Paper Nautilus. When you look inside you will see it does not have chambers like the Nautilus.
The shell is not a shell as we think of shells with a living animal attached. It is an egg case. The mother argonauta created it for the purpose of laying her eggs to protect her babies. The Greeks saw the mother octopus sailing around in the egg case and mistook her sail-like flaps as a means of movement and associated her with their mythical ship the Argo. This is how the name Argonauta came into being. They named the animal after the Argonauts. The Argonauts were Greek heroes who traveled by ship to obtain the golden fleece.
You do not see many Paper Nautiluses in collections. They are delicate and hard to obtain in good condition. At the present time I have some seconds that are reasonably priced . If you prefer, I have gem quality also.