paper nautilus

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of several cephalopod mollusks of the genus Argonauta that have eight arms, the female of which is much larger than the male and inhabits a paper-thin shell that serves as an egg case.

from The Century Dictionary.

• noun The paper-sailor or argonaut. See Argonaut, Argonautidæ and nautilus.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A pelagic octopus of genus Argonauta, found in warm seas, whose females produce a paper-thin egg case resembling a shell into which she deposits her eggs.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun cephalopod mollusk of warm seas whose females have delicate papery spiral shells