Nautilus (nawe-till-lus) is the common name of any marine creatures of the cephalopod family Nautilidae, the sole extant family of the suborder Nautilina.  It comprises six speices in two genera, the type of which is the genus Nautilus.  A nautilus has a large shell around its body.  The shell can be closed with a thick flap of skin called a hood.  A nautilus does not have arms, but it does have about 90 thin tentacles that it can stretch out of its shell.  These tentacles do not have suckers.  Nautiluses are predators and feed mainly on shrimp, small fish and crustaceans, which are captured by the tentacles.  The tentacles differ from those of other cephalopods.  They serve an adhesive function, sticking  to prey by virtue of their ridged surface - they lack tentacular pads.