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                                                                     EXHIBIT 3.1


                          CERTIFICATE OF INCORPORATION

                                       OF

                           MXP REINCORPORATION CORP.


              FIRST:  The name of the corporation is MXP Reincorporation Corp.
(the "Corporation").

              SECOND:  The address of the registered office of the Corporation
in the State of Delaware is 1209 Orange Street, Wilmington, County of New
Castle, Delaware 19801.  The name of the registered agent of the Corporation at
such address is The Corporation Trust Company.

              THIRD:  The purpose of the Corporation is to engage in any lawful
act or activity for which corporations may be organized under the General
Corporation Law of the State of Delaware (the "General Corporation Law").

              FOURTH:  The total number of shares of stock which the
Corporation shall have the authority to issue is 1,000 shares of common stock,
par value $.01 per share ("Common Stock").

              In the event of a voluntary or involuntary liquidation,
dissolution or winding up of the affairs of the Corporation and upon any
distribution of the assets of the Corporation in connection therewith, the
holders of Common Stock shall be entitled to receive all the assets of the
Corporation, tangible and intangible, of whatever kind available for
distribution to stockholders, ratably in proportion to the number of shares of
Common Stock held by them.

              Each holder of Common Stock shall have one vote in respect of
each share of Common Stock held by such holder on any matter submitted to the
stockholders.  Cumulative voting of shares of Common Stock is prohibited.

              FIFTH:  The business and affairs of the Corporation shall be
managed by or under the direction of the Board of Directors.  In furtherance
and not in limitation of the powers conferred by statute, the Board of
Directors is expressly authorized to adopt, amend or repeal the Bylaws of the
Corporation; provided, however, that the grant of such authority shall not
divest the stockholders of the power, nor limit their power to adopt, amend or
repeal the Bylaws.  The number of directors that shall constitute the whole
Board of Directors of the Corporation shall be as from time to time fixed by,
or





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in the manner provided in, the Bylaws of the Corporation.  The election of
directors need not be by written ballot, unless the Bylaws so provide.  In
addition to the authority and powers hereinabove or by statute conferred upon
the directors, the directors are hereby authorized and empowered to exercise
all such powers and do all such acts and things as may be exercised or done by
the Corporation, subject to the provisions of the General Corporation Law, this
Certificate of Incorporation and any Bylaws adopted by the stockholders of the
Corporation; provided, however, that no Bylaws hereafter adopted by the
stockholders of the Corporation shall invalidate any prior act of the directors
that would have been valid if such Bylaws had not been adopted.

              SIXTH:  No director of the Corporation shall be personally liable
to the Corporation or any of its stockholders for monetary damages for breach
of fiduciary duty as a director involving any act or omission of any such
director; provided, however, that the foregoing provision shall not eliminate
or limit the liability of a director (a) for any breach of the director's duty
of loyalty to the Corporation or its stockholders, (b) for acts or omissions
not in good faith or which involve intentional misconduct or a knowing
violation of law, (c) under Section 174 of the General Corporation Law, as the
same exists or hereafter may be amended, or (d) for any transaction from which
the director derived an improper personal benefit.  If the General Corporation
Law is amended after the date of filing of this Certificate of Incorporation to
authorize corporate action further limiting or eliminating the personal
liability of directors, then the liability of a director of the Corporation, in
addition to the limitation on personal liability provided for herein, shall be
limited to the fullest extent permitted by the General Corporation Law as so
amended.  Any repeal or modification of this Article Sixth by the stockholders
of the Corporation shall be prospective only, and shall not adversely affect
any limitation on the personal liability of a director of the Corporation
existing at the time of such repeal or modification.

              SEVENTH:  The Corporation expressly elects not to be governed by
Section 203 of the General Corporation Law, as the same exists or hereafter may
be amended.

              EIGHTH:  The name and mailing address of the sole incorporator
are as follows:

              NAME                                MAILING ADDRESS

       Brandon L. Jones                           Baker & Botts, L.L.P.
                                                  2001 Ross Avenue
                                                  Dallas, Texas  75201





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              NINTH:  The powers of the sole incorporator shall terminate upon
the filing of this Certificate of Incorporation.  The names and mailing
addresses of the persons who are to serve as directors of the Corporation until
the first annual meeting of stockholders or until their successors are elected
and qualify are as follows:


              NAME OF DIRECTOR                    MAILING ADDRESS

              I. Jon Brumley                      c/o MXP Reincorporation Corp.
                                                  1400 Williams Square West
                                                  5205 North O'Connor Boulevard
                                                  Irving, Texas 75039

              Stephen K. Gardner                  c/o MXP Reincorporation Corp.
                                                  1400 Williams Square West
                                                  5205 North O'Connor Boulevard
                                                  Irving, Texas 75039

              M. Garrett Smith                    c/o MXP Reincorporation Corp.
                                                  1400 Williams Square West
                                                  5205 North O'Connor Boulevard
                                                  Irving, Texas 75039



              IN WITNESS WHEREOF, the undersigned has executed this Certificate
of Incorporation as of April 2, 1997 in his capacity as sole incorporator.




                                                                                
                                                  /s/ BRANDON L. JONES
                                                  ------------------------------
                                                  Brandon L. Jones





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