An amendment executed under Section 20612 shall be deemed a continuation and an amendment, to the extent of any variation in the two contracts, of the district’s contract with respect to rights of all employees of the district under this system. Accumulated contributions held for or as having been made by the district and its employees and the assets derived from those contributions shall be transferred to the credit of the county superintendent of schools as a contracting agency. The liability of the district after the effective date of the amendment shall be as provided in former Section 20584, as amended by Chapter 857 of the Statutes of 1965.