EXHIBIT 3.18

                                     FORM OF

                          AMENDED AND RESTATED BY-LAWS

                                       OF

                               SVM OF TEXAS, INC.

                             (Adopted _______, 2003)

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                                   ARTICLE I.

                                  SHAREHOLDERS

               Section 1. The annual meeting of the shareholders of the
Corporation for the purpose of electing directors and for the transaction of
such other business as may properly be brought before the meeting shall be held
on such date, and at such time and place within or without the State of Texas,
as may be designated from time to time by the Board of Directors.

               Section 2. Annual meetings of shareholders shall be held, at a
date, time and place fixed by the Board of Directors and stated in the notice of
meeting, to elect a Board of Directors and to transact such other business as
may properly come before the meeting. Special meetings of the shareholders may
be called by (i) the Chairman of the Board of Directors of the Corporation or by
the Board of Directors pursuant to a resolution approved by the Board of
Directors or (ii) the holders of at least 25% in voting power of all shares of
the Corporation entitled to vote at such meeting. The purpose or purposes of the
proposed meeting shall be included in the notice setting forth such call.

               Section 3. Except as otherwise provided by law, the Amended and
Restated Articles of Incorporation or these By-Laws, notice of the time, place
and, in the case of a special meeting, the purpose or purposes of the meeting of
shareholders shall be given not earlier than sixty, nor less than ten days
previous thereto, to each shareholder of record entitled to vote at the meeting.
If mailed, such notice shall be deemed to be given when deposited in the United
States mail, postage pre-paid, directed to the shareholder at such address as
appears on the records of the Corporation.

               Section 4. Except as otherwise provided by law, the Amended and
Restated Articles of Incorporation or these By-Laws, the holders of a majority
in voting power of the stock issued and outstanding and entitled to vote
thereat, present in person or represented by proxy, shall constitute a quorum at
all meetings of the shareholders for the transaction of business. If at any
regularly called meeting of shareholders there be less than a quorum present,
the shareholders present may adjourn the meeting from time to time without
further notice other than announcement at the meeting until a quorum shall be
present or represented. At such adjourned meeting at which a quorum shall be
present or represented any business may be transacted which might have been
transacted at the original meeting. If the adjournment is for more than 30 days,
or if, after the adjournment, a new record date is fixed for the adjourned


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meeting, a notice of the adjourned meeting shall be given to each shareholder of
record entitled to vote at the meeting.

               Section 5. Unless otherwise restricted by the Amended and
Restated Articles of Incorporation or these By-Laws, any action required or
permitted to be taken by the holders of the common stock of the Corporation may
be taken without a meeting if a consent in writing setting forth the action so
taken is signed by the holders of all the shares entitled to vote with respect
to the action that is the subject of the consent.

               Section 6. When a quorum is present at any meeting, the vote of
the holders of a majority in voting power of the stock present in person or
represented by proxy and entitled to vote on the matter shall decide any
question brought before such meeting, unless the question is one upon which by
express provision of statute or of the Amended and Restated Articles of
Incorporation, these By-Laws or the rules or regulations of any stock exchange
applicable to the Corporation, a different vote is required, in which case such
express provision shall govern and control the decision of such question.

                                  ARTICLE II.

                               BOARD OF DIRECTORS

               Section 1. The Board of Directors of the Corporation shall
consist of at least one (1) director, or such other number of directors, as
shall from time to time be fixed exclusively by resolution of the Board of
Directors. Directors shall (except as hereinafter provided for the filling of
newly created directorships) be elected by the holders of a plurality of the
votes cast by holders of shares present in person or represented by proxy and
entitled to vote thereon. A majority of the total number of directors then in
office (but not less than one-third of the number of directors constituting the
entire Board of Directors) shall constitute a quorum for the transaction of
business and, except as otherwise provided by law or by the Corporation's
Amended and Restated Articles of Incorporation, the act of a majority of the
directors present at any meeting at which there is a quorum shall be the act of
the Board of Directors. Directors need not be shareholders.

               Section 2. Newly created directorships in the Board of Directors
that result from an increase in the number of directors shall be filled only by
a majority of the directors then in office, although less than a quorum, or by a
sole remaining director; and the directors so chosen shall hold office for a
term as set forth in the Amended and Restated Articles of Incorporation of the
Corporation. Directors may be removed for any reason by the affirmative vote of
at least a majority in voting power of all shares of the Corporation entitled to
vote generally in the election of directors.

               Section 3. Meetings of the Board of Directors shall be held at
such place within or without the State of Texas as may from time to time be
fixed by resolution of the Board or as may be specified in the notice of any
meeting. Regular meetings of the Board of Directors shall be held at such times
as may from time to time be fixed by resolution of the Board and special
meetings may be held at any time upon the call of the President or Chief
Executive Officer or a majority of the directors, by oral, or written notice
including, telegram, cablegram, telecopy or


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other means of electronic transmission, duly served on or sent or mailed to each
director at such director's address or telecopy number as shown on the books of
the Corporation not less than twenty-four hours before the special meeting. The
notice of any meeting need not specify the purposes thereof. A meeting of the
Board may be held without notice immediately after the annual meeting of
shareholders at the same place at which such meeting is held. Notice need not be
given of regular meetings of the Board held at times fixed by resolution of the
Board. Notice of any meeting need not be given to any director who shall attend
such meeting in person (except when the director attends a meeting for the
express purpose of objecting, at the beginning of the meeting, to the
transaction of any business because the meeting is not lawfully called or
convened), or who shall waive notice thereof, before or after such meeting, in
writing or by electronic transmission.

               Section 4. The Board of Directors may, by resolution adopted by a
majority of the whole Board, designate one or more committees, including,
without limitation, an Executive Committee, to have and exercise such power and
authority as the Board of Directors shall specify. In the absence or
disqualification of a member of a committee, the member or members thereof
present at any meeting and not disqualified from voting, whether or not he or
they constitute a quorum, may unanimously appoint another director to act at the
absent of disqualified member.

               Each committee may determine the procedural rules for meeting and
conducting its business and shall act in accordance therewith, except as
otherwise provided herein or required by law. Provision shall be made for notice
to members of all meetings; one-third of the members shall constitute a quorum
unless the committee shall consist of one or two members, in which event one
member shall constitute a quorum; and all matters shall be determined by a
majority vote of the members present at any meeting at which there is a quorum.

               Section 5. Unless otherwise restricted by the Amended and
Restated Articles of Incorporation or these By-Laws, any action required or
permitted to be taken at any meeting of the Board of Directors or of any
committee thereof may be taken without a meeting if all members of the Board or
committee, as the case may be, consent thereto in writing or by electronic
transmission, and the writing or writings or electronic transmission or
transmissions are filed with the minutes of proceedings of the Board of
Directors or committee, as the case may be in accordance with applicable law.

               Section 6. The members of the Board of Directors or any committee
thereof may participate in a meeting of such Board or committee, as the case may
be, by means of conference telephone or other communications equipment by means
of which all persons participating in the meeting can hear each other, and
participation in a meeting pursuant to this section shall constitute presence in
person at such a meeting.

               Section 7. The Board of Directors may establish policies for the
compensation of directors and for the reimbursement of the expenses of
directors, in each case, in connection with services provided by directors to
the Corporation.



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                                  ARTICLE III.

                                    OFFICERS

               Section 1. The Board of Directors shall elect officers of the
Corporation, which shall include a President or Chief Executive Officer and a
Secretary. The Board of Directors may also from time to time elect such other
officers (including one or more Vice Presidents, a Treasurer, one or more
Assistant Vice Presidents, one or more Assistant Secretaries and one or more
Assistant Treasurers) as it may deem proper or may delegate to any elected
officer of the Corporation the power to appoint and remove any such other
officers and to prescribe their respective terms of office, authorities and
duties. Any Vice President may be designated Executive, Senior or Corporate, or
may be given such other designation or combination of designations as the Board
of Directors may determine. Any two or more offices may be held by the same
person, except that one person shall not be both the President or Chief
Executive Officer and Secretary.

               Section 2. All officers of the Corporation elected by the Board
of Directors shall hold office for such term as may be determined by the Board
of Directors or until their respective successors are chosen and qualified. Any
officer may be removed from office at any time either with or without cause by
the affirmative vote of a majority of the members of the Board then in office,
and, in the case of appointed officers, by any elected officer upon whom such
power of removal shall have been conferred by the Board of Directors.

               Section 3. Each of the officers of the Corporation elected by the
Board of Directors or appointed by an officer in accordance with these By-Laws
shall have the powers and duties prescribed by law, by the By-Laws or by the
Board of Directors and, in the case of appointed officers, the powers and duties
prescribed by the appointing officer, and, unless otherwise prescribed by the
By-Laws or by the Board of Directors or such appointing officer, shall have such
further powers and duties as ordinarily pertain to that office.

               Section 4. Unless otherwise provided in these By-Laws, in the
absence or disability of any officer of the Corporation, the Board of Directors
may, during such period, delegate such officer's powers and duties to any other
officer or to any director and the person to whom such powers and duties are
delegated shall, for the time being, hold such office.

                                  ARTICLE IV.

                    INDEMNIFICATION OF DIRECTORS AND OFFICERS

               To the fullest extent permitted by the laws of the State of
Texas:

               Section 1. Each person who was or is made a party or is
threatened to be made a party to or is otherwise involved in any actual or
threatened action, suit or proceeding, whether civil, criminal, administrative
or investigative (hereinafter a "proceeding"), by reason of the fact that he or
she or a person of whom he or she is the legal representative is or was a
director or an officer of the Corporation or is or was serving at the request of
the corporation as a director, officer or trustee of another corporation,
partnership, joint venture, trust or other enterprise, including service with



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respect to an employee benefit plan (hereinafter an "indemnitee"), whether the
basis of such proceeding is alleged action in an official capacity as a
director, officer or trustee or in any other capacity while serving as a
director, officer or trustee, shall be indemnified and held harmless by the
corporation to the fullest extent authorized by the Texas Business Corporations
Act ("TBCA"), as the same exists or may hereafter be amended, against all
expense, liability and loss (including attorneys' fees, judgments, fines, ERISA
excise taxes or penalties and amounts paid or to be paid in settlement)
reasonably incurred or suffered by such indemnitee in connection therewith;
provided, however, that, except as provided in the By-Laws of the Corporation
with respect to proceedings to enforce rights to indemnification and
"advancement of expenses" (as defined below), the Corporation shall indemnify
any such indemnitee in connection with a proceeding (or part thereof) initiated
by such indemnitee only if such proceeding (or part thereof) was authorized by
the Board of Directors of the Corporation.

               Section 2. In addition to the right to indemnification conferred
in this Article IV, Section 1, an indemnitee shall also have the right to be
paid by the Corporation the reasonable expenses (including attorneys' fees)
incurred in defending any such proceeding in advance of its final disposition
(hereinafter an "advancement of expenses"); provided, however, that, if the TBCA
requires, an advancement of expenses incurred by an indemnitee in his or her
capacity as a director or officer (and not in any other capacity in which
service was or is rendered by such indemnitee, including, without limitation,
service to an employee benefit plan) shall be made only upon delivery to the
Corporation of: (1) a written affirmation by the indemnitee of his or her good
faith belief that he or she has met the standard of conduct necessary for
indemnification under the TBCA; and (2) a written undertaking (hereinafter an
"undertaking"), by or on behalf of such indemnitee, to repay all amounts so
advanced if it shall ultimately be determined by final judicial decision from
which there is no further right to appeal (hereinafter a "final adjudication")
that such indemnitee is not entitled to be indemnified for such expenses under
this Article IV or otherwise.

               Section 3. A director of the Corporation shall not be personally
liable to the Corporation or its shareholders for monetary damages for an act or
omission in the director's capacity as a director, except to the extent the
director is found liable (i) for any breach of the director's duty of loyalty to
the Corporation or its shareholders, (ii) for acts or omissions not in good
faith that constitute a breach of duty of the director to the Corporation, or
which involve intentional misconduct or a knowing violation of law, (iii) for
any transaction from which the director derived an improper personal benefit,
whether or not the benefit resulted from an action taken within the scope of the
director's office, or (iv) for an act or omission for which the liability of the
director is expressly provided by an applicable statute. Any repeal or
modification of this Article Eighth, Section (2) shall be prospective only, and
shall not adversely affect any elimination or limitation of the personal
liability of a director of the Corporation in respect of any act or omission
occurring prior to the time of such repeal or modification.

                                   ARTICLE V.

                              CERTIFICATES OF STOCK

               Section 1. The shares of stock of the Corporation shall be
represented by certificates signed by, or in the name of the Corporation by the
President or Chief Executive


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Officer or a Vice President, and by the Treasurer or an Assistant Treasurer or
the Secretary or an Assistant Secretary of the Corporation, or as otherwise
permitted by law, representing the number of shares registered in certificate
form. Any or all of the signatures on the certificate may be a facsimile.

               Section 2. Transfers of stock shall be made on the books of the
Corporation by the holder of the shares in person or by such holder's attorney
upon surrender and cancellation of certificates for a like number of shares, or
as otherwise provided by law with respect to uncertificated shares.

                                  ARTICLE VI.

                                 CORPORATE BOOKS

               The books of the Corporation may be kept outside of the State of
Texas at such place or places as the Board of Directors may from time to time
determine.

                                  ARTICLE VII.

                          CHECKS, NOTES, PROXIES, ETC.

               All checks and drafts on the Corporation's bank accounts and all
bills of exchange and promissory notes, and all acceptances, obligations and
other instruments for the payment of money, shall be signed by such officer or
officers or agent or agents as shall be hereunto authorized from time to time by
the Board of Directors. Proxies to vote and consents with respect to securities
of other corporations owned by or standing in the name of the Corporation may be
executed and delivered from time to time on behalf of the Corporation by the
President or Chief Executive Officer, or by any such officers as the Board of
Directors may from time to time determine.

                                 ARTICLE VIII.

                                   FISCAL YEAR

               The fiscal year of the Corporation shall be fixed by the Board of
Directors.

                                  ARTICLE IX.

                                 CORPORATE SEAL

               The corporate seal shall have inscribed thereon the name of the
Corporation. In lieu of the corporate seal, a facsimile thereof may be impressed
or affixed or reproduced.

                                   ARTICLE X.

                              FACSIMILE SIGNATURES

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               In addition to the provisions for use of facsimile signatures
elsewhere specifically authorized in these By-Laws, facsimile signatures of any
officer or officers of the Corporation may be used whenever and as authorized by
the Board of Directors or a committee thereof.

                                  ARTICLE XI.

                                   AMENDMENTS

               The Board of Directors shall be authorized to make, amend, alter,
change, add to or repeal these By-Laws without a shareholder vote in any manner
not inconsistent with the laws of the State of Texas, subject to the power of
the shareholders entitled to vote to amend, alter, change, add to or repeal
these By-Laws. Notwithstanding anything contained in these By-Laws to the
contrary, the affirmative vote of the holders of a majority in voting power of
all the shares of the Corporation entitled to vote generally in the election of
directors shall be required in order for the shareholders to amend, alter,
change, add to or repeal these By-Laws.