The Free On-line Dictionary of Computing (30 December 2018):

longitudinal parity

    An extra byte (or word) appended
   to a block of data in order to reveal corruption of the data.
   Bit n of this byte indicates whether there was an even or odd
   number of "1" bits in bit position n of the bytes in the
   block.  The parity byte is computed by XORing the data bytes
   in the block.  Longitudinal parity allows single bit errors to
   be detected.

   (1996-03-01)