Note:  Do not rely on this information. It is very old.

Paper Nautilus

Paper Nautilus, a Cephalopod belonging to the sub-order Octopoda, and of interest as the females have a delicate, one-chambered shell. This is secreted by two of the arms which are expanded into a membranous plate, which are closely attached to the hinder part of the body; the shell is therefore "pedal," and not, as in ordinary shell-fish "pallial" - i.e. secreted by the mantle. The Paper Nautilus lives on the open seas in the warmer parts of the world, and it was believed to use the two expanded arms as sails; the fact that the shell is keeled further helped to this delusion. The only fossil forms occur in the Pliocene deposits. The generic name is Argonauta.