The chambered nautilus (Nautilus pompilius) is a shelled cephalopod with rudimentary tentacles.

It is interesting as an evolutionary link between  mollusks that have shells -- like snails or clams -- 

and mollusks lacking external shells -- like the tentacled cephalopods (octopus, squid and cuttlefish).  

Specimens were captured at 800 foot depths, brought to the reef for viewing, and then released back at original depth.

(Short Drop Off, Palau, Micronesia)

mollusk; cephalopod; nautilus; chambered nautilus; Mollusca; Cephalopoda; sC Nautiloidea; Nautilida; Nautilidae; Nautilus pompilius