A cephalopod is any member of the molluscan class Cephalopoda; "head-feet"). These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot. Fishermen sometimes call them inkfish, referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology.
source:wikipedia\Image by: neurmadic aesthetic