Do cephalopods have a shell?

Cephalopods in the nautiloid group have external shells that are coiled in shape much the same way a snail shell is coiled; this is because they are a more primitive form of cephalopod. However, it is more common for modern cephalopods to have internal shells.  This is the case with the squid and the cuttlefish.  The octopus has no shell at all.