EXHIBIT A --------- AGREEMENT OF JOINT FILING In accordance with Rule 13d-1(k) under the Securities and Exchange Act of 1934, as amended, the undersigned hereby agree to the joint filing on behalf of each of them of a Statement on Schedule 13D, and...

                                                                      EXHIBIT A
                                                                      ---------


                            AGREEMENT OF JOINT FILING

         In accordance with Rule 13d-1(k) under the Securities and Exchange Act
of 1934, as amended, the undersigned hereby agree to the joint filing on behalf
of each of them of a Statement on Schedule 13D, and any amendments thereto, with
respect to the Common Stock, par value $0.01 per share, and Series E Preferred
Stock, par value $0.01 per share, of OptiMark Holdings, Inc. and that this
Agreement be included as an Exhibit to such filing.

         This Agreement may be executed in any number of counterparts, each of
which shall be deemed to be an original and all of which together shall be
deemed to constitute one and the same Agreement.

         IN WITNESS WHEREOF, each of the undersigned hereby executes this
Agreement as of January __, 2001.

                                             SOFTBANK CAPITAL PARTNERS LP
                                             By: SOFTBANK CAPITAL PARTNERS LLC,
                                                      General Partner


                                             By: /s/ Xxxxxx X. Xxxxxx
                                                --------------------------------
                                                  Name:    Xxxxxx X. Xxxxxx
                                                  Title:   Administrative Member


                                             SOFTBANK CAPITAL PARTNERS LLC,


                                             By: /s/ Xxxxxx X. Xxxxxx
                                                --------------------------------
                                                  Name:    Xxxxxx X. Xxxxxx
                                                  Title:   Administrative Member


                                             SOFTBANK CAPITAL PARTNERS
                                             INVESTMENT INC.


                                             By: /s/ Xxxxxx X. Xxxxxx
                                                --------------------------------
                                                   Name:    Xxxxxx X. Xxxxxx
                                                   Title:   Treasurer


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                                             XXXXXX X. XXXXXX


                                             By: /s/ Xxxxxx X. Xxxxxx
                                                --------------------------------
                                                    Name: Xxxxxx X. Xxxxxx


                                             XXXXXXX X. XXX


                                             By: /s/ Xxxxxxx X. Xxx
                                                --------------------------------
                                                    Name: Xxxxxxx X. Xxx


                                             SOFTBANK HOLDINGS INC.


                                             By: /s/ Xxxxxxx X. Xxxxx
                                                --------------------------------
                                                    Name: Xxxxxxx X. Xxxxx
                                                    Title:  Secretary


                                             SOFTBANK CORP.


                                             By: /s/ Xxxxxxx X. Xxxxx
                                                --------------------------------
                                                    Name: Xxxxxxx X. Xxxxx
                                                    Title:  Attorney-in-Fact


                                             XXXXXXXXX XXX


                                             By: /s/ Xxxxxxx X. Xxxxx
                                                --------------------------------
                                                    Name: Xxxxxxx X. Xxxxx
                                                    Title:  Attorney-in-Fact




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