\Ceph`a*lop"o*da\, n. pl. [NL., gr. Gr. ? head +
-poda: cf. F. c['e]phalopode.] (Zo["o]l.)
The highest class of Mollusca.
Note: They have, around the front of the head, a group of
      elongated muscular arms, which are usually furnished
      with prehensile suckers or hooks. The head is highly
      developed, with large, well organized eyes and ears,
      and usually with a cartilaginous brain case. The higher
      forms, as the cuttlefishes, squids, and octopi, swim
      rapidly by ejecting a jet of water from the tubular
      siphon beneath the head. They have a pair of powerful
      horny jaws shaped like a parrot's beak, and a bag of
      inklike fluid which they can eject from the siphon,
      thus clouding the water in order to escape from their
      enemies. They are divided into two orders, the
      Dibranchiata, having two gills and eight or ten
      sucker-bearing arms, and the Tetrabranchiata, with four
      gills and numerous arms without suckers. The latter are
      all extinct except the {Nautilus}. See {Octopus},
      {Squid}, {Nautilus}.