<PAGE>

                                                                     Exhibit 4.2

                               FORM OF DEBENTURES

      The Debentures are to be substantially in the following form and shall
bear the following legend required by Section 204 of the Indenture:

      THIS SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE
HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITORY OR A
NOMINEE THEREOF. THIS SECURITY MAY NOT BE EXCHANGED IN WHOLE OR IN PART FOR A
SECURITY REGISTERED, AND NO TRANSFER OF THIS SECURITY IN WHOLE OR IN PART MAY BE
REGISTERED IN THE NAME OF ANY PERSON OTHER THAN SUCH DEPOSITORY OR A NOMINEE
THEREOF, EXCEPT IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE.

No. -                                                      Principal Amount: $-
Issue Date: -

                          THE TRAVELERS COMPANIES, INC.

                6.25% FIXED-TO-FLOATING RATE JUNIOR SUBORDINATED
                               DEBENTURES DUE 2067

      THE TRAVELERS COMPANIES, INC., a corporation organized and existing under
the laws of Minnesota (hereinafter called the "COMPANY", which term includes any
successor corporation under the Indenture hereinafter referred to), for value
received, hereby promises to pay to CEDE & CO., or registered assigns, the
principal sum of - DOLLARS ($-) as may be revised from time to time on Schedule
I hereto and all accrued and unpaid interest thereof on March 15, 2037, or if
such day is not a Business Day, the following Business Day (the "SCHEDULED
MATURITY DATE") or any subsequent Interest Payment Date (as hereafter defined)
to the extent set forth in the First Supplemental Indenture. If that amount is
not paid in full on the Scheduled Maturity Date or any subsequent Interest
Payment Date, the remaining amount, together with accrued and unpaid interest,
will be due and payable on the Final Maturity Date. The Final Maturity Date will
be March 15, 2067, or if such day is not a Business Day, the following Business
Day.

      The Company further promises to pay interest on said principal sum from
and including March 12, 2007, or from and including the most recent interest
payment date on which interest has been paid or duly provided for, semi-annually
(subject to deferral as set forth herein) in arrears on March 15 and September
15 of each year, commencing September 15, 2007, at the rate of 6.25 % per annum
(computed on the basis of a 360-day year comprised of twelve 30-day months) to

<PAGE>


but excluding March 15, 2017, and thereafter to pay interest on said outstanding
principal sum quarterly in arrears on March 15, June 15, September 15, and
December 15 of each year (each such date and, together with such March 15 and
September 15 of each year, an "INTEREST PAYMENT DATE"), at a floating annual
rate equal to Three-Month LIBOR (as defined in the First Supplemental Indenture)
plus 2.215% (computed on the basis of a 360-day year and the actual number of
days elapsed), until the principal hereof shall have become due and payable,
plus Additional Interest, if any, until the principal hereof is paid or duly
provided for or made available for payment. Accrued interest that is not paid on
the applicable Interest Payment Date, including interest deferred pursuant to
Section 2.05 of the First Supplemental Indenture, will bear Additional Interest,
to the extent permitted by law, at the interest rate in effect from time to
time, from the relevant Interest Payment Date, compounded on each subsequent
Interest Payment Date. In the event that any Semi-Annual Interest Payment Date
on which interest is payable on this Security is not a Business Day, then a
payment of the interest payable on such date will be made on the next succeeding
day that is a Business Day (and, in the case of payments on or prior to March
15, 2017, without any interest or other payment in respect of any such delay)
with the same force and effect as if made on the date the payment was originally
payable. In the event that any Quarterly Interest Payment Date on which interest
is payable on this Security is not a Business Day, then a payment of the
interest payable on such date shall be postponed to the next succeeding day that
is a Business Day, provided that if such Business Day is in the next succeeding
calendar month, such Interest Payment Date shall be the immediately preceding
Business Day, and interest will accrue to but excluding the date that interest
is actually paid. A "Business Day" shall mean any day other than (i) a Saturday
or Sunday, (ii) a day on which banking institutions in The City of New York are
authorized or required by law or executive order to remain closed or (iii) a day
on which the corporate trust office of the Trustee, is closed for business. The
interest installment so payable, and punctually paid or duly provided for, on
any Interest Payment Date will, as provided in the Indenture, be paid to the
Person in whose name this Security (or one or more Predecessor Securities) is
registered at the close of business on the Regular Record Date for such interest
installment, which shall be March 1 or September 1, as the case may be,
immediately preceding such Interest Payment Date until March 15, 2017 (whether
or not a Business Day), and the 15th day preceding the Relevant Interest Payment
Date after March 15, 2017. Any such interest installment not so punctually paid
or duly provided for shall forthwith cease to be payable to the Holder on such
Regular Record Date and may either be paid to the Person in whose name this
Security (or one or more Predecessor Securities) is registered at the close of
business on a Special Record Date for the payment of such Defaulted Interest to
be fixed by the Trustee, notice whereof shall be given to Holders of Securities
of this series not less than 10 days prior to such Special Record Date, or be
paid at any time in any other lawful manner not inconsistent with the
requirements of any securities exchange on which the Securities of this series
may be listed, and upon such notice as may be required by such exchange, all as
more

<PAGE>


fully provided in said Indenture.

      So long as no Event of Default has occurred and is continuing, the Company
shall have the right at any time or from time to time during the term of this
Security to defer payment of interest on this Security for one or more
consecutive interest payment periods (each a "DEFERRAL PERIOD") that do not
exceed 10 years, during which Deferral Periods the Company shall have the right,
subject to Sections 2.05 and 2.06 of the First Supplemental Indenture, to make
partial payments of interest on any Interest Payment Date, and at the end of
which the Company shall pay all interest then accrued and unpaid (together with
Additional Interest thereon to the extent permitted by applicable law);
provided, however, that no Deferral Period shall extend beyond the Final
Maturity Date or the earlier repayment or redemption in full of the Securities.
Upon the termination of any Deferral Period and upon the payment of all deferred
interest then due, the Company may elect to begin a new Deferral Period, subject
to the above requirements. Deferred interest on the Security will bear interest
at the then applicable interest rate, compounded on each Interest Payment Date,
subject to applicable law. No interest shall be due and payable during a
Deferral Period except at the end thereof. Additional limitations may apply,
pursuant to Section 3.02 of the First Supplemental Indenture, if any Deferral
Period lasts longer than one year.

      So long as any Securities remain outstanding, if the Company has given
notice of its election to defer interest payments on the Securities but the
related Deferral Period has not yet commenced or a Deferral Period is
continuing, the Company shall not, and shall not permit any Subsidiary of the
Company to, (i) declare or pay any dividends or distributions, or redeem,
purchase, acquire or make a liquidation payment with respect to any shares of
the Company's capital stock, (ii) make any payment of principal of, or interest
or premium, if any, on or repay, purchase or redeem any debt securities of the
Company that rank upon the Company's liquidation on a parity with this Security
(including this Security, the "PARI PASSU SECURITIES" ), or junior in interest
to this Security or (iii) make any payments under any guarantee issued by the
Company of the securities of any Subsidiary if the guarantee ranks upon
liquidation on a parity with or junior to this Security (other than (a) any
purchase, redemption or other acquisition of shares of the Company's capital
stock in connection with (1) any employment contract, benefit plan or other
similar arrangement with or for the benefit of any one or more of its employees,
officers, directors, consultants or independent contractors, (2) the
satisfaction of the Company's obligations pursuant to any contract entered into
in the ordinary course of business prior to the beginning of the applicable
Deferral Period, (3) a dividend reinvestment or shareholder purchase plan, or
(4) the issuance of the Company's capital stock, or securities convertible into
or exercisable for such capital stock, as consideration in an acquisition
transaction entered into prior to the applicable Deferral Period, (b) any
exchange, redemption or conversion of any class or series of the Company's
capital stock, or the capital stock of one of its Subsidiaries, for any other
class or series of its capital stock, or of any class or series of its
indebtedness for any class or series of its capital stock,

<PAGE>


(c) any purchase of fractional interests in shares of the Company's capital
stock pursuant to the conversion or exchange provisions of such capital stock or
the securities being converted or exchanged, (d) any declaration of a dividend
in connection with any shareholder rights plan, or the issuance of rights, stock
or other property under any shareholder rights plan, or the redemption or
purchase of rights pursuant thereto, (e) any dividend in the form of stock,
warrants, options or other rights where the dividend stock or stock issuable
upon exercise of such warrants, options or other rights is the same stock as
that on which the dividend is being paid or ranks equally with or junior to such
stock, (f) any payment of current or deferred interest on Pari Passu Securities
that is made pro rata to the amounts due on such Pari Passu Securities
(including the this Security); provided that such payments are made in
accordance with Section 2.06(c) of the First Supplemental Indenture to the
extent it applies, and any payments of deferred interest on Pari Passu
Securities that, if not made, would cause the Company to breach the terms of the
instrument governing such Pari Passu Securities; or (g) any payment of principal
in respect of Pari Passu Securities having the same scheduled maturity date as
this Security, as required under a provision of such other Pari Passu Securities
that is substantially the same as the provisions in Section 2.02 of the First
Supplemental Indenture, and that is made on a pro rata basis among one or more
series of Pari Passu Securities (including this Security) having such a
provision. In addition, if any Deferral Period lasts longer than one year, the
restrictions on the Company's ability to redeem or purchase any of its
Qualifying APM Securities or any of its securities that on its bankruptcy or
liquidation rank pari passu or junior to such Qualifying APM Securities will
continue until the first anniversary of the date on which all deferred interest
on this Security has been paid.

      The Company shall give written notice of its election to begin or extend
any Deferral Period, to the Trustee and the Holders of this Security at least
one Business Day and not more than sixty Business Days before the next Interest
Payment Date. Notice of the Company's election of a Deferral Period shall be
given to the Trustee and each holder of this Security at such holder's address
appearing in the Security Register by first-class mail, postage prepaid.

      Payment of the principal of (and premium, if any) and interest on this
Security will be made at the office or agency of the Company maintained for that
purpose in the United States, in such coin or currency of the United States of
America as at the time of payment is legal tender for payment of public and
private debts; provided, however, that at the option of the Company payment of
interest may be made (i) by check mailed to the address of the Person entitled
thereto as such address shall appear in the Securities Register or (ii) by wire
transfer in immediately available funds at the bank account number as may be
designated by the Person entitled thereto as specified in the Securities
Register in writing not less than ten days before the relevant Interest Payment
Date.

      The indebtedness evidenced by this Security is, to the extent provided in

<PAGE>

the Indenture, subordinate and junior in right of payment to the prior payment
in full of all Senior Indebtedness, and this Security is issued subject to the
provisions of the Indenture with respect thereto. Each Holder of this Security,
by accepting the same, (a) agrees to and shall be bound by such provisions, (b)
authorizes and directs the Trustee on his behalf to take such actions as may be
necessary or appropriate to effectuate the subordination so provided and (c)
appoints the Trustee his attorney-in-fact for any and all such purposes. Each
Holder hereof, by his acceptance hereof, waives all notice of the acceptance of
the subordination provisions contained herein and in the Indenture by each
holder of Senior Indebtedness, whether now outstanding or hereafter incurred,
and waives reliance by each such holder upon said provisions.

      The Company and, by acceptance of this Security or a beneficial interest
in this Security, each Holder hereof and any person acquiring a beneficial
interest herein, agree that for United States federal, state and local tax
purposes it is intended that this Security constitute indebtedness.

      Reference is hereby made to the further provisions of this Security set
forth on the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

      Unless the certificate of authentication hereon has been executed by the
Trustee referred to on the reverse hereof by manual signature, this Security
shall not be entitled to any benefit under the Indenture or be valid or
obligatory for any purpose.

<PAGE>

      In Witness Whereof, the Company has caused this instrument to be duly
executed.

                                                 THE TRAVELERS COMPANIES, INC.

                                                 By:
                                                    ------------------------
                                                    Name:
                                                    Title:

                     TRUSTEE'S CERTIFICATE OF AUTHENTICATION

                                 This is one of the Securities of the
                                 series designated therein referred to
                                 in the within-mentioned Indenture.

                                                 THE BANK OF NEW YORK TRUST
                                                    COMPANY, N.A.

                                                 By:
                                                    -------------------------
                                                    Name:
                                                    Title: Authorized Signatory
                                                    Dated:

<PAGE>

                         (FORM OF REVERSE OF DEBENTURES)

      This Security is one of a duly authorized issue of securities of the
Company (herein called the "DEBENTURES"), issued and to be issued in one or more
series under the Junior Subordinated Indenture, dated as of March 12, 2007
(herein called the "BASE INDENTURE"), between the Company and The Bank of New
York Trust Company, N.A., as trustee (the "TRUSTEE"), as amended and
supplemented by the First Supplemental Indenture, dated as of March 12, 2007,
between the Company and the Trustee (the "FIRST SUPPLEMENTAL INDENTURE", and
together with the Base Indenture, the "INDENTURE"), to which Indenture and all
other indentures supplemental thereto reference is hereby made for a statement
of the respective rights, limitations of rights, duties and immunities
thereunder of the Trustee, the Company and the Holders of the Debentures, and of
the terms upon which the Debentures are, and are to be, authenticated and
delivered. By the terms of the Indenture, the Securities are issuable in series
that may vary as to amount, date of maturity, rate of interest, rank and in any
other respect provided in the Indenture.

      All terms used in this Security that are defined in the Indenture shall
have the meanings assigned to them in the Indenture.

      The Debentures shall be redeemable at the option of the Company in
accordance with the terms of the Indenture. In particular, the Debentures are
redeemable (i) in whole or in part at the option of the Company at any time
after the date hereof and (ii) in whole but not in part at any time within 90
days following the occurrence and during the continuation of a Tax Event or
Rating Agency Event, in each case at a Redemption Price equal to (1) in the case
of any redemption on or after March 15, 2017, 100% of the principal amount of
the Debentures being redeemed plus accrued and unpaid interest to the redemption
date or (2) in the case of any redemption prior to March 15, 2017, the greater
of (i) 100% of its principal amount plus accrued and unpaid interest to the
redemption date, or (ii) the Make-Whole Redemption Price; provided that if the
Debentures are not redeemed in whole, the Company may not affect such redemption
unless at least $25 million aggregate principal amount of the Debentures,
excluding any Debentures held by the Company or any of its affiliates, remains
outstanding after giving effect to such redemption.

      No sinking fund is provided for the Debentures.

      The Indenture contains provisions for satisfaction and discharge of the
entire indebtedness of this Security upon compliance by the Company with certain
conditions set forth in the Indenture.

      The Indenture permits, with certain exceptions as therein provided, the
Company and the Trustee at any time to enter into a supplemental indenture or
indentures for the purpose of modifying in any manner the rights and obligations

<PAGE>

of the Company and of the Holders of the Securities, with the consent of the
Holders of not less than a majority in principal amount of the Outstanding
Securities to be affected by such supplemental indenture. The Indenture also
contains provisions permitting Holders of specified percentages in principal
amount of the Securities at the time Outstanding, on behalf of the Holders of
all Securities, to waive compliance by the Company with certain provisions of
the Indenture and certain past defaults under the Indenture and their
consequences. Any such consent or waiver by the Holder of this Security shall be
conclusive and binding upon such Holder and upon all future Holders of this
Security and of any Security issued upon the registration of transfer hereof or
in exchange herefor or in lieu hereof, whether or not notation of such consent
or waiver is made upon this Security.

      As provided in and subject to the provisions of the Indenture, if an Event
of Default with respect to the Securities at the time Outstanding occurs and is
continuing, then and in every such case the Trustee or the Holders of not less
than 25% in principal amount of the Outstanding Securities may declare the
entire principal amount and all accrued but unpaid interest of all the
Securities to be due and payable immediately, by a notice in writing to the
Company (and to the Trustee if given by Holders), provided that the payment of
principal and interest (including any Additional Interest) on such Securities
shall remain subordinated to the extent provided in Article Eleven of the
Indenture.

      No reference herein to the Indenture and no provision of this Security or
of the Indenture shall alter or impair the obligation of the Company, which is
absolute and unconditional, to pay the principal of (and premium, if any) and
interest on this Security at the times, place and rate, and in the coin or
currency, herein prescribed.

      As provided in the Indenture and subject to certain limitations therein
set forth, the transfer of this Security is registrable in the Securities
Register, upon surrender of this Security for registration of transfer at the
office or agency of the Company maintained under Section 1002 of the Indenture
duly endorsed by, or accompanied by a written instrument of transfer in form
satisfactory to the Company and the Securities Registrar duly executed by, the
Holder hereof or his attorney duly authorized in writing, and thereupon one or
more new Securities, of authorized denominations and for the same aggregate
principal amount, will be issued to the designated transferee or transferees. No
service charge shall be made for any such registration of transfer or exchange,
but the Company may require payment of a sum sufficient to cover any tax or
other governmental charge payable in connection therewith.

      Prior to due presentment of this Security for registration of transfer,
the Company, the Trustee and any agent of the Company or the Trustee shall treat
the Person in whose name this Security is registered as the owner hereof for all
purposes, whether or not this Security be overdue, and neither the Company, the
Trustee nor any such agent shall be affected by notice to the contrary.

<PAGE>

      The Securities are issuable only in registered form without coupons in
minimum denominations of $1,000 and any integral multiples of $1,000 in excess
thereof. As provided in the Indenture and subject to certain limitations therein
set forth, Securities are exchangeable for a like aggregate principal amount of
Securities of a different authorized denomination, as requested by the Holder
surrendering the same.

      The Company and, by its acceptance of this Security or a beneficial
interest therein, the Holder of, and any Person that acquires a beneficial
interest in, this Security agree to treat for United States Federal income tax
purposes (i) the Securities as indebtedness of the Company, and (ii) the stated
interest on the Securities as ordinary interest income that is includible in the
Holder's or beneficial owner's gross income at the time the interest is paid or
accrued in accordance with the Holder's or beneficial owner's regular method of
tax accounting, and otherwise to treat the Securities as described in the
Prospectus.

      THE INDENTURE AND THIS SECURITY SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

      This is one of the Securities referred to in the within mentioned
Indenture.

<PAGE>

                                   ASSIGNMENT

FOR VALUE RECEIVED, the undersigned assigns and transfers this Security to:

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

        (Insert assignee's social security or tax identification number)

_______________________________________________________________________________

_______________________________________________________________________________

                    (Insert address and zip code of assignee)

agent to transfer this Security on the books of the Securities Registrar. The
agent may substitute another to act for him or her.

Dated:                                              Signature:

                                                    Signature Guarantee:

     (Sign exactly as your name appears on the other side of this Security)

Signatures must be guaranteed by an "eligible guarantor institution" meeting the
requirements of the Securities Registrar, which requirements include membership
or participation in the Security Transfer Agent Medallion Program ("STAMP") or
such other "signature guarantee program" as may be determined by the Securities
Registrar in addition to, or in substitution for, STAMP, all in accordance with
the Securities Exchange Act of 1934, as amended.

<PAGE>

                                                                      SCHEDULE I

                     SCHEDULE OF PRINCIPAL AMOUNT REDUCTIONS

Principal amount of Debentures outstanding represented by this Security as of
March 12, 2007: $1,000,000,000

      Thereafter, the following decreases have been made:

<TABLE>
<CAPTION>
  Date of          Principal Amount                          Notation Made by
Redemption or        Redeemed or        Principal Amount    or on Behalf of the
 Repurchase          Repurchased            Remaining             Trustee
-------------      ----------------     ----------------    -------------------
<S>                <C>                  <C>                 <C>

</TABLE>