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                                                                    Exhibit 10.4
                                 PROMISSORY NOTE

$29,825                                         Dated: April 11, 2001
                                                New York, New York

         FOR VALUE RECEIVED, the undersigned, OPTIMARK HOLDINGS, INC. a Delaware
corporation, ("OPTIMARK") promises to pay to the order of SOFTBANK Capital
Advisors Fund LP, a Delaware limited partnership ("SOFTBANK"), the principal sum
of Twenty Nine Thousand Eight Hundred Twenty-Five and NO/100 DOLLARS ($29,825),
or such lesser principal amount plus interest, in lawful, immediately available
money of the United States of America.

         This Promissory Note ("NOTE") is issued by OptiMark pursuant to that
certain Convertible Loan Agreement dated as of April 11, 2001, (the "LOAN
AGREEMENT") between OptiMark and Softbank. Capitalized terms not otherwise
defined in this Note shall have the meaning set forth in the Loan Agreement,
which definitions are incorporated herein. The terms of the Loan Agreement are
also incorporated herein.

         OptiMark further agrees as follows:

         1. INTEREST RATE. Interest on the outstanding principal balance of this
Note shall accrue at the rate of ten percent (10%) per annum, based on a year of
360 days and actual days elapsed. Interest shall be compounded quarterly, shall
accrue from the Closing Date until the Loan is paid in full and shall be added
to principal as specified in the Loan Agreement. Upon the occurrence and during
the continuance of an Event of Default, interest on the outstanding principal
balance of this Note shall accrue at the Default Rate specified in Section 4.2
of the Loan Agreement and shall also be compounded quarterly However, in no
event shall the interest rate exceed the maximum rate permitted by law. Interest
shall be payable on the Maturity Date specified below.

         2. PAYMENT OF PRINCIPAL AND INTEREST. The outstanding principal balance
of this Note, together with all accrued but unpaid interest, shall be due and
payable on July 10, 2001 (the "MATURITY DATE"). The outstanding principal
balance due on this Note shall be determined as specified in Section 3.2 of the
Loan Agreement. The principal, interest and other sums due on this Note or under
the Loan Agreement shall be reflected by Softbank's records which will be prima
facie evidence of the computation of the amounts owing by OptiMark to Softbank,
absent manifest error.

         3. LOAN AGREEMENT AND PREPAYMENT. This Note is issued pursuant to the
terms of the Loan Agreement and is secured by the Collateral. Voluntary
prepayments of this Note may be made without penalty.

         4. DEFAULT. If an Event of Default shall occur, then all amounts due or
to become due under this Note or under the Loan Agreement or any of the Related
Documents shall become, or may be declared, immediately due and payable, all as
further provided in the Loan Agreement.
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         5. MAXIMUM AMOUNT OF INTEREST. Notwithstanding any contrary provision,
the total liability of OptiMark for payment of interest hereunder shall not
exceed the maximum amount of interest permitted by law, and if any payment made
by the OptiMark includes interest in excess of such a maximum amount, Softbank
shall at any time before or after default apply such excess to the reduction of
principal hereunder.

         6. CONVERSION. The outstanding principal balance of the Loan together
with accrued but unpaid interest may be converted into Next Round Preferred
Stock pursuant to the Loan Agreement.

         7. WAIVERS BY OPTIMARK. Subject to any provisions to the contrary in
the Loan Agreement, OptiMark waives presentment for payment, demand, notice of
nonpayment, notice of protest and protest of this Note, and all notices in
connection with the delivery, acceptance, or dishonor of this Note. OptiMark
agrees that (a) if for any reason any amount due hereunder is paid by cashier's,
certified teller's check or other check, there shall be no discharge of
OptiMark's obligation until said check be finally paid by the issuer thereof;
and (b) OptiMark shall have waived any rights to any accord and satisfaction of
any now or hereafter existing claim in dispute between Softbank and OptiMark (or
any of their respective successors and assigns), all of which provisions and
rights are hereby waived.

         8. NO WAIVER BY SOFTBANK. Softbank shall not by any act of omission or
commission be deemed to waive any of its rights or remedies under this Note or
the Loan Agreement unless such waiver shall be in writing and signed by
Softbank, and then only to the extent specifically set forth therein.

         9. COSTS AND FEES. OptiMark agrees to pay to Softbank all Costs and
Fees (including without limitation, reasonable attorneys' fees) payable under
the provisions of the Loan Agreement, including but not limited to Section 4.1
thereof, all of which provisions are incorporated herein by this reference.

         10. APPLICATION OF ARTICLE 3. OptiMark and Softbank agree that the
provisions of Article 3 of the Uniform Commercial Code of New York pertaining to
instruments shall be applied to this Note, even if this Note is not deemed to be
an "INSTRUMENT" or a "NEGOTIABLE INSTRUMENT" thereunder, except that no assignee
of this Note shall have the status of a "HOLDER-IN-DUE COURSE" under that
Article.

         11. GOVERNING LAW; VENUE. This Note shall be governed by and construed
in accordance with the internal laws of the State of New York. Without impairing
the other agreements made by OptiMark in the Loan Agreement, OptiMark hereby
irrevocably makes the agreements set forth in Sections 9.5 (Governing Law;
Venue) of the Loan Agreement.


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                                          OPTIMARK HOLDINGS, INC.
                                          a Delaware corporation

                                          By  /s/ Robert J. Warshaw
                                             ----------------------------------

                                          Its  CEO
                                             ----------------------------------


                      [Signature Page to Promissory Note]