lateral line system
  n  (Zoology) a system of sensory organs in fishes and aquatic amphibians consisting of a series of cells on the head and along the sides of the body that detect pressure changes and vibrations
  Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014