EXHIBIT 4.6
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                         COMMON SECURITY CERTIFICATE

          THIS COMMON SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES
ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"), OR ANY STATE SECURITIES LAWS
OR ANY OTHER APPLICABLE SECURITIES LAW. NEITHER THIS COMMON SECURITY NOR ANY
INTEREST OR PARTICIPATION HEREIN MAY BE REOFFERED, SOLD, ASSIGNED,
TRANSFERRED, PLEDGED, ENCUMBERED OR OTHERWISE DISPOSED OF IN THE ABSENCE OF
SUCH REGISTRATION OR UNLESS SUCH TRANSACTION IS EXEMPT FROM, OR NOT SUBJECT
TO, REGISTRATION.

          THE HOLDER OF THIS COMMON SECURITY BY ITS ACCEPTANCE HEREOF AGREES TO
OFFER, SELL OR OTHERWISE TRANSFER THIS COMMON SECURITY, PRIOR TO THE DATE (THE
"RESALE RESTRICTION TERMINATION DATE") WHICH IS TWO YEARS AFTER THE LATER OF THE
ORIGINAL ISSUANCE DATE HEREOF AND THE LAST DATE ON WHICH GREATER BAY BANCORP
(THE "CORPORATION") OR ANY "AFFILIATE" OF THE CORPORATION WAS THE OWNER OF THIS
COMMON SECURITY (OR ANY PREDECESSOR OF THIS COMMON SECURITY) ONLY (A) TO THE
CORPORATION, (B) PURSUANT TO A REGISTRATION STATEMENT WHICH HAS BEEN DECLARED
EFFECTIVE UNDER THE SECURITIES ACT, (C) SO LONG AS  THIS COMMON SECURITY IS
ELIGIBLE FOR RESALE PURSUANT TO RULE 144A UNDER THE SECURITIES ACT ("RULE
144A"), TO A PERSON IT REASONABLY BELIEVES IS A "QUALIFIED INSTITUTIONAL BUYER"
(AS DEFINED IN RULE 144A) THAT PURCHASES FOR ITS OWN ACCOUNT OR FOR THE ACCOUNT
OF A QUALIFIED INSTITUTIONAL BUYER TO WHOM NOTICE IS GIVEN THAT THE TRANSFER IS
BEING MADE IN RELIANCE ON RULE 144A, (D) TO AN INSTITUTIONAL "ACCREDITED
INVESTOR" WITHIN THE MEANING OF SUBPARAGRAPH (A)(1), (2), (3) OR (7) OF RULE 501
UNDER THE SECURITIES ACT THAT IS ACQUIRING THIS COMMON SECURITY FOR ITS OWN
ACCOUNT, OR FOR THE ACCOUNT OF SUCH AN INSTITUTIONAL ACCREDITED INVESTOR, FOR
INVESTMENT PURPOSES AND NOT WITH A VIEW TO, OR FOR OFFER OR SALE IN CONNECTION
WITH, ANY DISTRIBUTION IN VIOLATION OF THE SECURITIES ACT, OR (E) PURSUANT TO
ANY OTHER AVAILABLE EXEMPTION FROM THE REGISTRATION REQUIREMENTS UNDER THE
SECURITIES ACT, SUBJECT TO THE RIGHT OF GBB CAPITAL II (THE "TRUST") AND THE
CORPORATION PRIOR TO ANY SUCH OFFER, SALE OR TRANSFER (i) PURSUANT TO CLAUSE (D)
OR (E) TO REQUIRE THE DELIVERY OF AN OPINION OF COUNSEL, CERTIFICATIONS AND/OR
OTHER INFORMATION SATISFACTORY TO EACH OF THEM, AND (ii) PURSUANT TO CLAUSE (D)
TO REQUIRE THAT TRANSFEROR DELIVER TO THE TRUST A LETTER FROM THE TRANSFEREE
SUBSTANTIALLY IN THE FORM OF ANNEX A TO THE OFFERING MEMORANDUM DATED AUGUST 7,
1998. SUCH HOLDER FURTHER AGREES THAT IT WILL DELIVER TO EACH PERSON TO WHOM
THIS COMMON SECURITY IS TRANSFERRED A NOTICE SUBSTANTIALLY TO THE EFFECT OF THIS
LEGEND.

 
                  Certificate Evidencing Common Securities

                                     of

                               GBB CAPITAL II

                       Floating Rate Common Securities
               (liquidation amount $1,000 per Common Security)

          GBB CAPITAL II, a statutory business trust created under the laws of
the State of Delaware (the "Trust"), hereby certifies that Greater Bay Bancorp
(the "Holder") is the registered owner of 928 common securities of the Trust
representing undivided beneficial interests in the assets of the Trust
designated the Floating Rate Common Securities (liquidation amount $1,000 per
Common Security) (the "Common Securities").  Subject to the terms of the Trust
Agreement (as defined below), the Common Securities are transferable on the
books and records of the Trust, in person or by a duly authorized attorney, upon
surrender of this Certificate duly endorsed and in proper form for transfer. The
designation, rights, privileges, restrictions, preferences and other terms and
provisions of the Common Securities represented hereby are issued and shall in
all respects be subject to the provisions of the Amended and Restated Trust
Agreement of the Trust dated as of August 12, 1998, as the same may be amended
from time to time (the "Trust Agreement"), including the designation of the
terms of the Common Securities as set forth in Annex I to the Trust Agreement.
Capitalized terms used but not defined herein shall have the meaning given them
in the Trust Agreement. The Sponsor will provide a copy of the Trust Agreement,
the Common Securities Guarantee and the Indenture (including any supplemental
indenture) to a Holder without charge upon written request to the Trust at its
principal place of business.

          Upon receipt of this Certificate, the Holder is bound by the Trust
Agreement and is entitled to the benefits thereunder and to the benefits of the
Common Securities Guarantee to the extent provided therein.

          By acceptance hereof, the Holder agrees to treat, for United States
federal income tax purposes, the Debentures as indebtedness and the Common
Securities as evidence of indirect beneficial ownership in the Debentures.

          IN WITNESS WHEREOF, the Trust has executed this certificate this 12th
day of August, 1998.

                                    GBB CAPITAL II


                                    By:   /s/ Steven C. Smith
                                          ----------------------------------
                                          Steven C. Smith
                                          Administrative Trustee

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          Distributions on each Common Security will be payable at a rate per
annum, reset quarterly, equal to 3-month LIBOR (as defined in the Trust
Agreement) plus 150 basis points (the "Coupon Rate"), such rate being the rate
of interest payable on the Debentures to be held by the Property Trustee.
Distributions in arrears for more than one quarterly period will bear interest
thereon compounded quarterly at the Coupon Rate (to the extent permitted by
applicable law). Pursuant to the Registration Rights Agreement, in certain
limited circumstances the Debenture Issuer will be required to pay Liquidated
Damages (as defined in the Registration Rights Agreement) with respect to the
Debentures. The term "Distributions", as used herein, includes such cash
distributions and any and all such interest and Liquidated Damages, if any,
payable unless otherwise stated. A Distribution is payable only to the extent
that payments are made in respect of the Debentures held by the Property Trustee
and to the extent the Property Trustee has funds legally available therefor.

          Distributions on the Common Securities will be cumulative, will accrue
from the most recent date to which Distributions have been paid or, if no
Distributions have been paid, from August 12, 1998 and will be payable quarterly
in arrears, on March 15, June 15, September 15 and December 15, of each year,
commencing December 15, 1998, except as otherwise described below. Distributions
will be computed on the basis of the actual number of days elapsed in such
period and a 360-day year. As long as no Event of Default has occurred and is
continuing under the Indenture, the Debenture Issuer has the right under the
Indenture to defer payments of interest by extending the interest payment period
at any time and from time to time on the Debentures for a period not exceeding
20 consecutive calendar quarterly periods, including the first such quarterly
period during such extension period (each an "Extension Period"), provided that
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no Extension Period shall end on a date other than an Interest Payment Date for
the Debentures or extend beyond the Maturity Date of the Debentures. As a
consequence of such deferral, Distributions will also be deferred.
Notwithstanding such deferral, quarterly Distributions will continue to
accumulate with interest thereon (to the extent permitted by applicable law, but
not at a rate exceeding the rate of interest then accruing on the Debentures) at
the applicable periodic Coupon Rate compounded quarterly during any such
Extension Period. Prior to the termination of any Extension Period, the
Debenture Issuer may further defer payments of interest by further extending
such Extension Period; provided that such Extension Period, together with all
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such previous and further extensions within such Extension Period, may not (i)
exceed 20 consecutive quarterly periods, including the first quarterly period
during such Extension Period, (ii) end on a date other than an Interest Payment
Date for the Debentures or (iii) extend beyond the Maturity Date of the
Debentures. Payments of accrued Distributions will be payable to Holders as they
appear on the books and records of the Trust on the record date immediately
preceding the end of the Extension Period. Upon the termination of any Extension
Period and the payment of all amounts then due, the Debenture Issuer may
commence a new Extension Period, subject to the above requirements.

          Subject to the receipt by the Sponsor of any and all required
regulatory approvals and to certain other conditions set forth in the Trust
Agreement and the Indenture, the Property Trustee may, at the direction of the
Sponsor, at any time dissolve the Trust and cause the Debentures to be
distributed to the Holders of the Securities in liquidation of the Trust or,
simultaneously with any redemption of the Debentures, cause a Like Amount of the
Securities to be redeemed by the Trust.

                                       3

 
          The Common Securities shall be redeemable as provided in the Trust
Agreement.

          Under certain circumstances, the rights of the holders of the Common
Securities shall be subordinate to the rights of the holders of the Capital
Securities, as provided in the Trust Agreement.

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