Cephalopods Cephalopods are a class of fast-swimming mollusk . Some have a hard external shell, but most do not. There are about 650 living cephalopods and over 7,500 known extinct cephalopods. The foot of the cephalopod is a cluster of tentacles that connects directly to the head. The brain, the eyes, and the other sensory organs are well-developed.
Cephalopods breathe using gills.
Many can also eject a cloud of ink to confuse enemies. Blue Ring Octopus A small but very venomous octopus from warm reefs in Australia and nearby regions. Architeuthis or Giant Squid Giant Squid swim deep in the oceans. They have ten arms and their eyes are the size of basketballs. Cuttlefish Cuttlefish are cephalopods with relatively short legs, a fin along the entire mantle, and an internal cuttlebone.