Cephalopods
Cephalopoda is the most morphologically and behaviorally complex class in phylum Mollusca. Cephalopoda means "head foot" and this group has the most complex brain of any invertebrate. Cephalopods are characterized by a completely merged head and foot, with a ring of arms and/or tentacles surrounding the head. The arms, tentacles, and funnel are all derivatives of the foot.