Phylum Mollusca
Class Cephalopoda  (means Head-Foot)

Although some Cephalopods have shells, Octopi do not.    These ocean-dwellers move by
expelling water out of a funnel, a process called jet propulsion.   They have
eight arms covered in suction cups and a horny beak, are able to change color
rapidly, and have the most complex brain of any invertebrate. It serves them well in the hunt for prey, since they live on other animals.