High time resolution magnetic field measurements adjacent to the boundary of the distant magnetotail plasma sheet have been analyzed. The nature of the changes in the field between the lobe and the plasma sheet is consistent with the boundary being a slow mode shock. The crossing times are relatively long (~ 30 sec) implying a shock thickness estimated to be approximately 103 km. An increase in the entropy of the electrons is consistent with dissipation at the shock. Reasonable shock normal directions are derived and may be used to determine the location of the spacecraft relative to the reconnection or merging region. It is suggested that a foreshock exists in which upstream wave and particle phenomena are occurring.