Source : WordNet®

hippocampus
     n 1: a complex neural structure (shaped like a sea horse)
          consisting of gray matter and located on the floor of
          each lateral ventricle; intimately involved in
          motivation and emotion as part of the limbic system; has
          a central role in the formation of memories
     2: seahorses [syn: {genus Hippocampus}]
     [also: {hippocampi} (pl)]

hippocampi
     See {hippocampus}