SUBROUTINE XREV(Z,NX,NY)
      DIMENSION Z(NX,NY)
C
      DO 2000   IY=1,NY
      DO 1000   IX=1,NX/2
      T=Z(IX,IY)
      Z(IX,IY)=Z(NX-IX+1,IY)
      Z(NX-IX+1,IY)=T
 1000 CONTINUE
 2000 CONTINUE
C
      RETURN
      END