but octopi don't have shells?!...

Today after an enjoyable day of climbing, I returned home to a drizzle and a puzzle.  A friend of mine in Japan messaged me about a confusion of hers.  Seems she found some shells on the beach in Japan and was told that they are octopus shells.  Now she took high school biology like everybody else and knows that octopi don't have shells(BTW I was of that mind as well).  it is one of the features that separate them from other mollusks.  So she asked me, being her closest octopus loving friend.  Well after first thinking that it must have been a lost in translation moment she produced pictures of the shell.  Well based off of this info I eventually discovered the Paper nautilus, Argonauta argo.   It isn't a nautilus like the name suggests ( much like a starfish isnt a fish ), but I believe the name references the shell that is produced by the female ( males do not do this ) as it prepares a home for its eggs ( it being an open ocean dwelling octopus it cant hide the eggs in reefs ).  Its eyes are particularly interesting as all other octopus eyes I've seen have a horizontal pupil ( goats and some sheep also have this feature ) which I've learned helps to increase peripheral depth perception.  The nautilus however, has pinhole eyes and as far as I can tell, they are the only group that do.  Also unlike other octopi, the female doesn't die after mating and releasing eggs ( the male however does die ).  So... I have learned of a new octopus, which i must say is neither boring nor mundane.  I will have to learn more about this conundrum of a cephalopod.  Thanks Sara!