FORM OF PROXY FOR PETROCORP INCORPORATED

                                                                    EXHIBIT 99.3


                            PETROCORP INCORPORATED

     PROXY SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS OF PETROCORP
INCORPORATED FOR A SPECIAL MEETING OF STOCKHOLDERS TO BE HELD ON        , 2001

  The undersigned shareholder of PetroCorp Incorporated, a Texas corporation
("PetroCorp"), hereby appoints Frederic Dormant and Tamara Wagman, and either of
them, the lawful attorneys and proxies of the undersigned, with several powers
of substitution, to vote all shares of common stock, par value $0.01 per share,
of PetroCorp which the undersigned is entitled to vote at the Special Meeting of
Shareholders to be held on            , 2001, and any adjournments thereof:

    1. To consider and vote upon a proposal to approve the merger agreement
       among PetroCorp, Southern Mineral Corporation and PetroCorp Acquisition
       Company, which is a newly-formed, wholly-owned subsidiary of PetroCorp,
       and the transactions contemplated by the merger agreement, including the
       merger and the issuance of PetroCorp common stock, the amendment to
       PetroCorp's bylaws increasing the number of directors by two, and the
       appointment of designees of the Southern Mineral board to fill the two
       newly created vacancies.

    [ ]  FOR                   [ ]  AGAINST                       [ ]  ABSTAIN


    2. In the discretion of the proxy holders, to transact such other business
       as may properly come before the meeting or any adjournment or
       postponement thereof.

           (Continued and to be dated and signed on the other side)

    THIS PROXY WILL BE VOTED AS DIRECTED HEREIN BY THE UNDERSIGNED. IN THE
ABSENCE OF SPECIFIC INSTRUCTIONS, PROXIES WILL BE VOTED FOR APPROVAL AND
ADOPTION OF THE MERGER AGREEMENT AND IN THE DISCRETION OF THE PROXY HOLDERS AS
TO ANY OTHER MATTERS THAT MAY PROPERLY COME BEFORE THE MEETING OR ANY


ADJOURNMENT OR POSTPONEMENT THEREOF. IF THIS PROXY IS VOTED "AGAINST" THE
PROPOSAL TO APPROVE AND ADOPT THE MERGER AGREEMENT, SUCH DISCRETIONARY AUTHORITY
WILL NOT BE USED TO VOTE THIS PROXY FOR THE ADJOURNMENT OR POSTPONEMENT OF THE
MEETING TO PERMIT FURTHER SOLICITATION OF PROXIES. THE BOARD OF DIRECTORS IS NOT
AWARE OF ANY MATTER WHICH IS TO BE PRESENTED FOR ACTION AT THE MEETING OTHER
THAN THE MATTERS SET FORTH HEREIN.

    THE BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT THE SHAREHOLDERS OF AMFM
VOTE FOR THE APPROVAL AND ADOPTION OF THE MERGER AGREEMENT.

                                          Signature:

                                          --------------------------------

                                          --------------------------------

                                          Date:                     , 2001

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                                          NOTE: Please sign exactly as name
                                          appears hereon. Joint owners should
                                          each sign. When signing in a fiduciary
                                          or representative capacity, please
                                          give full title as such.