EXHIBIT 4.3(a)

                                     FORM OF

                          SUPPLEMENTAL INDENTURE NO. 1

                                 By and Between

                         SENIOR HOUSING PROPERTIES TRUST

                                       and

                       STATE STREET BANK AND TRUST COMPANY

                               As of June 21, 2001

             SUPPLEMENTAL TO THE INDENTURE DATED AS OF JUNE 21, 2001

                      ------------------------------------

                         SENIOR HOUSING PROPERTIES TRUST

            10.125% Junior Subordinated Debentures due June 15, 2041

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<TABLE>
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                                TABLE OF CONTENTS
<S>                <C>                                                                                           <C>

ARTICLE I           DEFINITIONS...................................................................................1
         1.1.       Definition of Terms...........................................................................1
ARTICLE II          GENERAL TERMS AND CONDITIONS OF THE DEBENTURES................................................3
         2.1.       Designation and Principal Amount..............................................................3
         2.2.       Stated Maturity...............................................................................4
         2.3.       Form and Payment; Minimum Transfer Restriction................................................4
         2.4.       Procedure for Distribution of Debentures to Holders of Trust Preferred
                    Securities; Global Debenture; Depositary......................................................4
         2.5.       Interest......................................................................................5
         2.6.       Applicability of Discharge, Defeasance and Covenant Defeasance Provisions.....................6
ARTICLE III         REDEMPTION OF THE DEBENTURES..................................................................6
         3.1.       Tax Event or Investment Company Event Redemption..............................................6
         3.2.       Optional Redemption by Company................................................................6
         3.3.       Payment of Redemption Price if Preferred Securities are Book-entry............................6
ARTICLE IV          EXTENSION OF INTEREST PAYMENT PERIOD..........................................................6
         4.1.       Extension of Interest Payment Period..........................................................7
         4.2.       Notice of Extension...........................................................................7
ARTICLE V           COVENANTS.....................................................................................8
         5.1.       Additional Covenants of the Company...........................................................8
ARTICLE VI          EVENTS OF DEFAULT.............................................................................9
         6.1.       Events of Default.............................................................................9
ARTICLE VII         SUBORDINATION OF DEBENTURES...................................................................9
         14.1.      Agreement to Subordinate.....................................................................10
         14.2.      When Distribution Must be Paid Over..........................................................10
         14.3.      Note By Company..............................................................................11
         14.4.      Subrogation..................................................................................11
         14.5.      Relative Rights..............................................................................11
         14.6.      Subordination May Not Be Impaired by Company.................................................11
         14.7.      Distribution or Notice to Representative.....................................................11
         14.8.      Authorization of Trustee to Effectuate Subordination of the Debentures.......................12
ARTICLE VIII        EFFECTIVENESS................................................................................12
ARTICLE IX          MISCELLANEOUS................................................................................12
         9.1.       Separablity..................................................................................12
         9.2.       Supplemental Indenture Controls..............................................................12
         9.3.       Governing Law................................................................................12
         9.4.       Counterparts.................................................................................12


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                                       i


<PAGE>
         This SUPPLEMENTAL INDENTURE NO. 1 (this "Supplemental  Indenture") made
and entered into as of June 21, 2001 between SENIOR HOUSING  PROPERTIES TRUST, a
Maryland real estate investment trust (the "Company"), and STATE STREET BANK AND
TRUST COMPANY, a Massachusetts trust company, as Trustee (the "Trustee"),

                                WITNESSETH THAT:

         WHEREAS,  the Company and the Trustee have  executed  and  delivered an
Indenture,  dated as of June 21, 2001 (the "Base  Indenture" and,  together with
this Supplemental Indenture, the "Indenture") to provide for the future issuance
of the Company's junior  subordinated  debt securities (the  "Securities") to be
issued from time to time in one or more series;

         WHEREAS,  pursuant  to the  terms of the Base  Indenture,  the  Company
desires to provide for the  establishment  of a series of its Securities,  to be
known as its  10.125%  Junior  Subordinated  Debentures  due June 15,  2041 (the
"Debentures"),  the  form  and  substance  of such  Debentures  and  the  terms,
provisions  and  conditions  thereof  to be set  forth as  provided  in the Base
Indenture and this Supplemental Indenture;

         WHEREAS,  SNH Capital Trust I, a Maryland business trust (the "Trust"),
has offered to the purchasers  (the  "Underwriters")  named in Schedule A to the
Underwriting  Agreement,  dated June 18,  2001 (the  "Underwriting  Agreement"),
among  the  Representatives  of the  several  Underwriters,  SNH  Capital  Trust
Holdings  as sponsor of the Trust (the  "Sponsor"),  the Trust and the  Company,
$25,000,000   aggregate  liquidation  amount  of  its  10.125%  Trust  Preferred
Securities (the "Trust Preferred Securities"), representing undivided beneficial
interests in the assets of the Trust,  and proposes to invest the proceeds  from
the sale of the Trust  Preferred  Securities,  together with the proceeds of the
sale by the Trust to the  Sponsor,  as  designee  of the  Company,  of  $773,200
aggregate liquidation amount of its Common Securities,  in $25,773,200 aggregate
principal amount of the Debentures; and

         WHEREAS,  pursuant to the  Underwriting  Agreement,  the Trust has also
granted to the Underwriters an option to acquire up to an additional  $3,750,000
aggregate  liquidation  amount  of  its  Trust  Preferred  Securities  to  cover
overallotments,  and proposes to invest the proceeds from any sale of such Trust
Preferred Securities, together with the proceeds of the sale by the Trust to the
Sponsor,  as designee of the Company,  of up to an additional $116,000 aggregate
liquidation amount of its Common  Securities,  up to an $3,866,000 in additional
aggregate principal amount of the Debentures;

         NOW, THEREFORE,  in consideration of the purchase and acceptance of the
Debentures by the Trust,  and for the purpose of setting  forth,  as provided in
the Base  Indenture,  the form and  substance of the  Debentures  and the terms,
provisions and  conditions  thereof,  the Company  covenants and agrees with the
Trustee as follows:

                                   ARTICLE I
                                   DEFINITIONS

         1.1. Definition of Terms. The following definitions supplement, and, to
the extent  inconsistent  with,  replace the  definitions  in Section 101 of the
Indenture:
<PAGE>

         (a)  the  term  "Trust  Preferred  Securities"  as  used  herein  means
"Preferred Securities" as such term is used in the Trust Agreement; and

         (b) the  following  terms have the meanings  given to them in the Trust
Agreement:  (i) Business  Day,  (ii) Closing  Date,  (iii)  Distributions,  (iv)
Guarantee, (v) Investment Company Event, (vi) Liquidation Amount, (vii) Property
Trustee, (viii) Regular Trustee, (ix) Sponsor and (x) Tax Event.

         "Additional Interest" has the meaning specified in Section 2.5(a).

         "Additional Sums" means such additional  amounts as may be necessary in
order that the amount of Distributions due and payable by the Trust on the Trust
Preferred  Securities and Common Securities that at any time remain  outstanding
in  accordance  with the terms  thereof  shall not be reduced as a result of any
additional taxes, duties, assessments and other governmental charges of whatever
nature,  imposed by the United States  government or any other taxing  authority
(but not  including  withholding  taxes  imposed on  holders  of such  Preferred
Securities and Common Securities).

         "Common Security" means an undivided  beneficial interest in the assets
of the Trust.

         "Common  Stock" means common  shares of beneficial  interest,  $.01 par
value per share, of the Company,  or any other stock of any class of the Company
which has no  preference  in respect of dividends  or of amounts  payable in the
event of any voluntary or involuntary liquidation,  dissolution or winding up of
the Company and which is not subject to redemption by the Company.

         "Coupon Rate" has the meaning specified in Section 2.5(a).

         "Extension Period" has the meaning specified in Section 4.1(a).

         "Global Debenture" has the meaning specified in Section 2.4(a).

         "Interest Payment Date" has the meaning specified in Section 2.5.

         "Debentures"  has the meaning  specified in the second  recital to this
Supplemental Indenture.

         "Optional Redemption Price" has the meaning specified in Section 3.2.

         "Obligations" has the meaning specified in Section 14.1(a).

         "Record Date" has the meaning specified in Section 2.5(a).

         "Representatives" has the meaning specified in Section 14.2.

         "Securities"  has the meaning  specified  in the first  recital to this
Supplemental Indenture.

         "Senior  Indebtedness of the Company" means (i) any indebtedness of the
Company for  borrowed or  purchased  money,  whether or not  evidenced by bonds,
debentures, notes or other

                                      -2-
<PAGE>

written  instruments,  (ii) obligations of the Company for  reimbursement  under
letters of credit, banker's acceptances, security purchase facilities or similar
facilities  issued for the account of the  Company,  (iii) any  indebtedness  or
other obligations of the Company with respect to commodity contracts  (including
but not limited to contracts  in the spot,  forward and  markets,  options,  and
contracts  for   differences),   interest  rate   commodity  and  currency  swap
agreements,  cap,  floor  and  collar  agreements,  currency  spot  and  forward
contracts,  and other  similar  agreements or  arrangements  designed to protect
against  fluctuations in commodity prices,  currency exchange or interest rates,
and (iv) any guarantees,  endorsements  (other than by endorsement of negotiable
instruments  for collection in the ordinary course of business) or other similar
contingent  obligations  in respect of obligations of others of a type described
in (i), (ii) or (iii) above,  whether or not such  obligation is classified as a
liability on a balance sheet  prepared in  accordance  with  generally  accepted
accounting  principles,  in each case listed in (i), (ii),  (iii) and (iv) above
whether  outstanding on the date of execution of this Supplemental  Indenture or
thereafter  incurred,  other  than  obligations  ranking  on a  parity  with the
Debentures or ranking junior to the Debentures;  provided, however, that "Senior
Indebtedness  of the  Company"  does not include  obligations  of the Company to
trade creditors.

         "Special Event" has the meaning specified in Section 3.1.

         "Special Event Redemption  Price" has the meaning  specified in Section
3.1.

         "Trust"  has  the  meaning  specified  in the  third  recital  to  this
Supplemental Indenture.

         "Trust Agreement" means the Amended and Restated Trust Agreement of SNH
Capital Trust I dated as of June 21, 2001 among SNH Capital Trust  Holdings,  as
Sponsor,  State Street Bank and Trust Company, as Property Trustee,  the Regular
Trustees  named  therein  and the  holders,  from  time to  time,  of  undivided
beneficial  interests  in the assets of the Trust,  as the same may be modified,
amended  or  supplemented  from time to time,  including  all  exhibits  and the
provisions of the Trust  Indenture Act that are deemed to be a part of the Trust
Agreement.

         "Trust  Preferred  Securities"  has the meaning  specified in the third
recital to this Supplemental Indenture.

         "Trust  Securities" means the Common Securities and the Trust Preferred
Securities.

         "Underwriters"  has the meaning  specified in the third recital to this
Supplemental Indenture.

         "Underwriting Agreement" has the meaning specified in the third recital
to this Supplemental Indenture.

                                   ARTICLE II
                 GENERAL TERMS AND CONDITIONS OF THE DEBENTURES

         2.1.  Designation and Principal Amount.  There is hereby authorized one
series  of  Securities,  to  be  designated  the  "10.125%  Junior  Subordinated
Debentures due June 15, 2041," in the initial  aggregate  principal amount of up
to  $29,639,200,  subject to the right of the  Company to reopen such series for
issuances  of  additional  securities  of such  series and except as

                                      -3-
<PAGE>

provided in Section 306 of the Base Indenture. The Debentures (together with the
Trustee's  certificate of authentication)  shall be substantially in the form of
Exhibit  A  hereto,  which  is  hereby  incorporated  in and made a part of this
Supplemental Indenture.

         2.2. Stated Maturity. The Stated Maturity of the Debentures is June 15,
2041, provided, however, the Debentures may be earlier redeemed at the option of
the Company as provided in Article III below.

         2.3. Form and Payment; Minimum Transfer Restriction.

         (a) The  Debentures  shall be issued to the  Property  Trustee in fully
registered  definitive form without coupons in minimum  denominations of $25 and
integral  multiples  of $25 in excess  thereof.  Principal  and  interest on the
Debentures  issued in  definitive  form will be  payable,  the  transfer of such
Debentures will be registrable  and such  Debentures  will be  exchangeable  for
Debentures bearing identical terms and provisions at the Corporate Trust Office;
provided,  however,  that  payment of interest  may be made at the option of the
Company by check mailed to the registered holder at such address as shall appear
in the Register. Notwithstanding the foregoing, so long as the registered holder
of any Debentures is the Property  Trustee,  the payment of the principal of and
interest  (including  Additional  Interest and Additional  Sums, if any) on such
Debentures  held by the Property  Trustee will be made at such place, or by wire
transfer of immediately available funds to such account, as may be designated by
the  Property  Trustee.  The Register  for the  Debentures  shall be kept at the
Corporate Trust Office,  and the Trustee is hereby  appointed  registrar for the
Debentures.

         (b) The  Debentures  may be  transferred  or exchanged  only in minimum
denominations  of $25 and integral  multiples of $25 in excess thereof,  and any
attempted transfer, sale or other disposition of Debentures in a denomination of
less than $25 shall be deemed to be void and of no legal effect whatsoever,  and
any such transferee  shall be deemed not to be the holder of such Debentures for
any purpose,  including but not limited to the receipt of payments in respect of
such  Debentures  and  such  transferee  shall  be  deemed  to have no  interest
whatsoever in such Debentures.

         2.4.  Procedure  for  Distribution  of  Debentures  to Holders of Trust
Preferred Securities; Global Debenture; Depositary. If distributed to holders of
Trust Preferred  Securities pursuant to Section 9.4 of the Trust Agreement,  the
Debentures  will be  issued  to  such  holders  in the  same  form as the  Trust
Preferred  Securities  that  such  Debentures  replace  in  accordance  with the
following procedures:

         (a) So long as Debentures are eligible for book-entry  settlement  with
the  Depositary,  the Debentures  will initially be issued in the form of one or
more registered  global  securities  without coupons ("Global  Debentures") that
will be  deposited  with,  or on  behalf  of,  a  Depositary,  who  shall be the
Depositary for the Trust Preferred Securities.  Initially,  the Depositary shall
be The Depository  Trust Company  ("DTC"),  or any successor  Depositary for the
Trust Preferred Securities,  and the Global Debenture shall be registered in the
name of DTC's nominee, Cede & Co. Except under the circumstance described below,
the Debentures will not be issuable in definitive  form.  Unless and until it is
exchanged in whole or in part for the individual Debentures represented thereby,
a Global Debenture may not be transferred  except as

                                      -4-
<PAGE>

a whole by DTC to a  nominee  of DTC or by a  nominee  of DTC to DTC or  another
nominee of DTC or by DTC or any nominee of DTC to a successor  depositary or any
nominee of such successor.

         (b) So long as DTC or its nominee is the  registered  owner of a Global
Debenture,  DTC or such nominee, as the case may be, will be considered the sole
owner or holder of the Debentures  represented by such Global  Debenture for all
purposes under this Supplemental Indenture. Except as described below, owners of
beneficial  interest in Debentures  evidenced by a Global  Debenture will not be
entitled to have any of the  individual  Debentures  represented  by such Global
Debenture  registered in their names, will not receive or be entitled to receive
physical  delivery of any such  Debentures  in  definitive  form and will not be
considered   the  owners  or  holders   thereof  under  the  Indenture  or  this
Supplemental Indenture.

         (c) If DTC is at any time  unwilling,  unable or ineligible to continue
as depositary and a successor  depositary is not appointed by the Company within
90 days, the Company will issue individual Debentures in exchange for the Global
Debenture or Global Debentures  representing such Debentures.  In addition,  the
Company  may at  any  time  and  in its  sole  discretion,  subject  to  certain
limitations  set  forth  in the  Indenture,  determine  not to have  any of such
Debentures represented by one or more Global Debentures and, in such event, will
issue  individual  Debentures  in exchange  for the Global  Debenture  or Global
Debentures representing the Debentures.  Individual Debentures so issued will be
issued in denominations of $25 and integral multiples thereof.

         (d) If the Debentures are distributed to holders of the Trust Preferred
Securities  pursuant to the terms of the Trust  Agreement,  the Company will use
its best efforts to list the  Debentures on the New York Stock  Exchange or such
other  stock  exchange  or  other  organization,  if any,  on  which  the  Trust
Securities are then listed.

         (e) Each Global Debenture shall bear substantially the following legend
on the face thereof:

         UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF
         THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO ISSUER
         OR ITS AGENT FOR REGISTRATION OF TRANSFER,  EXCHANGE,  OR PAYMENT,  AND
         ANY  CERTIFICATE  ISSUED IS  REGISTERED IN THE NAME OF CEDE & CO. OR IN
         SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED  REPRESENTATIVE OF DTC
         (AND ANY  PAYMENT IS MADE TO CEDE & CO. OR TO SUCH  OTHER  ENTITY AS IS
         REQUESTED  BY AN  AUTHORIZED  REPRESENTATIVE  OF  DTC),  ANY  TRANSFER,
         PLEDGE,  OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON
         IS WRONGFUL INASMUCH AS THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN
         INTEREST HEREIN.

         2.5.  Interest.  (a) Each  Debenture  will bear interest at the rate of
10.125% per annum (the "Coupon Rate") from and including June 21, 2001 until the
principal thereof becomes due and payable, and will bear interest on any overdue
principal at the Coupon Rate and (to the extent that payment of such interest is
enforceable under applicable law) on any overdue  installment of interest at the
Coupon Rate ("Additional  Interest") until paid, compounded

                                      -5-
<PAGE>

quarterly,  payable  (subject  to the  provisions  of Article IV)  quarterly  in
arrears  on the 15th day of  September,  December,  March  and June of each year
(each,  an "Interest  Payment  Date"),  commencing  on September 15, 2001 to the
Person in whose name such  Debenture is  registered  at the close of business on
the Record Date next preceding such Interest Payment Date. The "Record Date" for
payment of interest  will be one Business Day before the Interest  Payment Date,
unless such Debenture is registered to a holder other than the Property  Trustee
or a nominee of the  Depositary,  in which case the Record  Date for  payment of
interest  will be the  fifteenth  calendar  day before the  applicable  Interest
Payment Date, whether or not a Business Day. Until  liquidation,  if any, of the
Trust,  each Debenture will be held in the name of the Property Trustee in trust
for the benefit of the holders of the Trust Securities.

         (b) The amount of  interest  payable for any period will be computed on
the basis of a 360-day year of twelve 30-day months.  In the event that any date
on which  interest  is payable on the  Debentures  is not a Business  Day,  then
payment of interest payable on such date will be made on the next succeeding day
which is a Business Day (and without any interest or other payment in respect of
any such  delay),  with the same  force  and  effect as if made on the date such
payment was originally payable.

         2.6.  Applicability  of Discharge,  Defeasance and Covenant  Defeasance
Provisions. The Discharge and Covenant Defeasance provisions in Article Thirteen
of the Base Indenture will apply to the Debentures. The Defeasance provisions in
Article Thirteen of the Base Indenture will not apply to the Debentures

                                  ARTICLE III
                          REDEMPTION OF THE DEBENTURES

         3.1. Tax Event or Investment  Company Event Redemption.  If a Tax Event
or  Investment  Company  Event  (either a "Special  Event")  shall  occur and be
continuing,  the Company may redeem the  Debentures  at any time within 180 days
following the occurrence of that Special  Event,  in whole but not in part, at a
redemption  price (the "Special  Event  Redemption  Price") equal to 100% of the
principal  amount of the Debentures plus accrued and unpaid interest  thereon to
the Redemption Date.

         3.2. Optional Redemption by Company.  The Company shall have the option
to redeem the  Debentures  at any time on or after June 15, 2006, in whole or in
part, at a redemption price (the "Optional  Redemption  Price") equal to 100% of
the principal  amount of the Debentures plus accrued and unpaid interest thereon
to the Redemption Date.

         3.3.   Payment  of  Redemption   Price  if  Preferred   Securities  are
Book-entry.  If the Preferred  Securities are in book-entry-only  form, in order
for the Property  Trustee to meet the  obligation set forth in Section 4.2(d) of
the Trust  Agreement,  the  Company  shall  deposit  with the  Trustee an amount
sufficient to pay the Special Event Redemption Price or the Optional  Redemption
Price,  as the case may be, by 10:00 a.m.,  New York City time, on the date such
Special Event Redemption Price or Optional Redemption Price, as the case may be,
is to be paid

                                   ARTICLE IV
                      EXTENSION OF INTEREST PAYMENT PERIOD

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<PAGE>

         4.1. Extension of Interest Payment Period.

         (a) So long as no  Event  of  Default  under  Section  501 of the  Base
Indenture (as  supplemented by Section 6.1 of this  Supplemental  Indenture) has
occurred and is continuing, the Company shall have the right, at any time during
the term of the  Debentures,  from time to time to defer the payment of interest
and  Additional  Sums, if any, by extending the interest  payment period of such
Debentures  for a period not exceeding 20  consecutive  quarters (an  "Extension
Period").  No Extension  Period shall extend  beyond the Stated  Maturity of the
Debentures.  To the extent  permitted  by  applicable  law,  accrued  and unpaid
interest and Additional  Sums, the payment of which has been deferred because of
an Extension  Period imposed  pursuant to this Section 4.1, will bear Additional
Interest compounded  quarterly.  At the end of the Extension Period, the Company
shall pay all interest then accrued and unpaid on the Debentures,  including any
Additional  Interest and Additional  Sums, if applicable,  to the holders of the
Debentures in whose names the  Debentures  are registered in the Register on the
first  Record  Date  preceding  the  end of the  Extension  Period.  Before  the
termination  of any Extension  Period,  the Company may elect to (i) shorten the
Extension  Period or (ii) further  extend such Extension  Period,  provided that
such period together with all such further  extensions  thereof shall not exceed
20  consecutive  quarters,  or extend  beyond the Stated  Maturity.  At any time
following the  termination  of any Extension  Period and upon the payment of any
accrued and unpaid Additional Interest and Additional Sums, if applicable,  then
due,  the  Company  may elect to begin a new  Extension  Period,  subject to the
foregoing requirements.  No interest or Additional Sums shall be due and payable
during an Extension Period, except at the end thereof.

         (b) During any such Extension Period, the Company shall not (i) declare
or pay any dividends or distributions on, or redeem, purchase, acquire or make a
liquidation  payment with respect to, any of the Company's  shares of beneficial
interest,  (ii) make any payment of principal of or interest or premium, if any,
on, or repay,  repurchase or redeem any  indebtedness  or debt securities of the
Company  that  rank on a parity  with or junior  to the  Debentures  in right of
payment or (iii) make any  guarantee  payments  with respect to any guarantee by
the Company of  indebtedness or debt securities of any Subsidiary of the Company
if such  guarantee  ranks on parity with or junior to the Debentures in right of
payment  (other than (A)  dividends or  distributions  payable  solely in Common
Stock,  (B)  any  reclassification  of any  class  of the  Company's  shares  of
beneficial  interest,  (C) any  declaration of a dividend in connection with the
implementation  of a plan  of the  Company  providing  for the  issuance  by the
Company to all  holders  of its Common  Stock of rights  entitling  the  holders
thereof to  subscribe  for or  purchase  shares of Common  Stock or any class or
series of preferred  shares,  which rights are (x) deemed to be transferred with
such shares of Common Stock, (y) issued in respect of future issuances of Common
Stock and (z) not  exercisable  until the  occurrence  of a  specified  event or
events (a "Rights Plan"), (D) the issuance of any shares of beneficial  interest
of the Company  under any Rights Plan or the  redemption  or  repurchase  of any
rights  distributed  pursuant to a Rights Plan, (E) payments under the Guarantee
relating to the Trust  Preferred  Securities,  and (F) purchases of Common Stock
issued under,  or issued  pursuant to rights issued under,  any of the Company's
benefit plans for its trustees, officers, employees,  consultants or advisors or
the  directors,  officers,  employees,  consultants or advisors of the Company's
advisor).

         4.2. Notice of Extension.

                                      -7-
<PAGE>

         (a) If the  Property  Trustee  is the  only  registered  Holder  of the
Debentures  at the time the  Company  elects  to  begin,  shorten  or  extend an
Extension  Period,  the Company  shall give written  notice to the Trust and the
Trustee of its election to begin,  shorten or extend any Extension  Period on or
before the earlier of (i) one  Business  Day before the Record Date for the next
succeeding  Interest  Payment Date or (ii) subject to  applicable  law and stock
exchange  rules,  the date the Trust is required to give notice of an  Extension
Period to the New York Stock Exchange or any other securities  exchange or other
applicable self-regulatory organization where the Trust Preferred Securities are
then listed.  The Company  shall cause the Trust to give notice of the Company's
election to begin,  shorten or extend an Extension Period to the holders of such
Trust Preferred Securities.

         (b) If the Property Trustee is not the only Holder of the Debentures at
the time the Company elects to begin, shorten or extend an Extension Period, the
Company shall give the Holders of the Debentures,  the Regular  Trustees and the
Trustee  written  notice of its  election  to  begin,  shorten  or  extend  such
Extension  Period at least 10 Business Days prior to the earlier of (i) the next
succeeding  Interest  Payment Date or (ii) subject to  applicable  law and stock
exchange  rules,  the date the Trust is required to give notice of an  Extension
Period to the New York Stock Exchange or any other securities  exchange or other
applicable self-regulatory organization where the Trust Preferred Securities are
then listed.

         (c) The quarter in which any notice is given pursuant to paragraphs (a)
or (b) of  this  Section  4.2  shall  be  counted  as one of the 20  consecutive
quarters permitted in the maximum Extension Period permitted under Section 4.1.

                                   ARTICLE V
                                    COVENANTS

         5.1. Additional  Covenants of the Company. In addition to the covenants
of the Company set forth in Article Ten of the Base  Indenture,  for the benefit
of the Holders of the Debentures:

         (a) The  Company  covenants  and agrees  (i) to  maintain  directly  or
indirectly 100% ownership of the Common Securities; provided that any successors
or assigns of the Company  permitted  by the Base  Indenture  may succeed to the
Company's ownership of the Common Securities, (ii) not to voluntarily terminate,
wind-up or liquidate the Trust,  except (A) in connection with a distribution of
the Debentures to the holders of the Trust  Preferred  Securities in liquidation
of the Trust or (B) in connection with any merger, consolidation or amalgamation
of the Trust permitted by the Trust  Agreement,  and (iii) to use its reasonable
efforts,  consistent  with the terms and provisions of the Trust  Agreement,  to
cause the Trust to  remain  classified  as a  grantor  trust for  United  States
Federal income tax purposes.

         (b) The  Company  covenants  and agrees  that if and so long as (i) the
Trustee is the Holder of all the  Debentures on behalf of the Trust and (ii) the
Company has elected, and has not revoked such election,  to pay Additional Sums,
the  Company  shall pay to the  Trust  the  Additional  Sums in  respect  of the
Preferred Securities and Common Securities.

                                      -8-
<PAGE>

                                   ARTICLE VI
                                EVENTS OF DEFAULT

         6.1.  Events of Default.  With respect to the  Debentures  issued under
this  Supplemental  Indenture,  Section  501 of the  Base  Indenture  is  hereby
replaced in its entirety as follows:

         "Event of Default" means any one of the following  events (whatever the
reason for such Event of Default  and  whether or not it shall be  voluntary  or
involuntary  or be effected  by  operation  of law or pursuant to any  judgment,
decree  or  order  of  any  court  or  any  order,  rule  or  regulation  of any
administrative or governmental body):

         (a) default in the payment of any  interest  upon the  Debentures  when
such interest  becomes due and payable,  and  continuance  of such default for a
period of 30 days, except during a during an Extension Period; or

         (b) default in the payment of the principal of the Debentures when they
become due and payable at their Maturity; or

         (c) default in the  performance  of, or breach of, any  covenant of the
Company in the Indenture  (other than a covenant a default in whose  performance
or whose breach is elsewhere  in this Section  specifically  dealt with or which
has been expressly  included in the Indenture solely for the benefit of a series
of Securities  other than the  Debentures),  and  continuance of such default or
breach for a period of 60 days after  there has been  given,  by  registered  or
certified  mail, to the Company by the Trustee or to the Company and the Trustee
by the Holders of at least a majority  in  principal  amount of the  Outstanding
Debentures a written notice  specifying  such default or breach and requiring it
to be remedied and stating that such notice is a "Notice of Default"  hereunder;
or

         (d) the Company or any Significant Subsidiary pursuant to or within the
meaning of any Bankruptcy Law (i) commences a voluntary  case,  (ii) consents to
the entry of an order for relief  against it in an  involuntary  case,  or (iii)
consents to the appointment of a Custodian of it or for all or substantially all
of its property, or

         (e) a court of competent  jurisdiction  enters an order or decree under
any  Bankruptcy  Law  that:  (i)  is  for  relief  against  the  Company  or any
Significant  Subsidiary in an involuntary case, (ii) appoints a Custodian of the
Company or any Significant  Subsidiary or for all or substantially all of either
of  its  property,  or  (iii)  orders  the  liquidation  of the  Company  or any
Significant  Subsidiary,  and the order or decree remains unstayed and in effect
for 90 days.

                                  ARTICLE VII
                           SUBORDINATION OF DEBENTURES

         Article  Fourteen  of the Base  Indenture  shall read as  follows  with
respect to Debentures issued under this Supplemental Indenture:

         14.1. Agreement to Subordinate. Each Holder of Debentures covenants and
agrees by its acceptance thereof, that the obligation of the Company to make any
payment on account of

                                      -9-
<PAGE>

the principal of and interest on the  Debentures  (the  "Obligations")  shall be
subordinate  and junior in right of payment to the Company's  obligations to the
holders of Senior Indebtedness of the Company.

         (a)  In  the  case  of  any   bankruptcy,   insolvency,   receivership,
conservatorship,  reorganization, readjustment of debt, marshaling of assets and
liabilities or similar proceedings or any dissolution, liquidation or winding-up
of or relating to the Company as a whole, whether voluntary or involuntary,  all
obligations  of  the  Company  due  or  to  become  due  to  holders  of  Senior
Indebtedness  of the Company  shall be  entitled to be paid in full,  in cash or
other permitted consideration,  or otherwise provided for, before any payment of
the Obligations shall be made by the Company.

         (b) In the event and during the  continuation of any default beyond any
grace period in the payment of principal of or interest on or any other monetary
amounts due any Senior  Indebtedness,  or in the event that any event of default
with respect to any Senior  Indebtedness  shall have  occurred and be continuing
and shall have resulted in such Senior  Indebtedness  becoming or being declared
due and payable  prior to the date on which it would  otherwise  have become due
and  payable,  unless and until such  event of  default  shall have been  cured,
waived or  remedied or shall have  ceased to exist and such  acceleration  shall
have been  rescinded or annulled or all amounts due on such Senior  Indebtedness
are paid in full in cash or other permitted consideration, or otherwise provided
for, then no payment of the Obligations shall be made by the Company.

         14.2.  When  Distribution  Must be Paid  Over.  In the  event  that the
Trustee or any Holder of Debentures receives from the Company any payment of any
Obligations  at a time  when  the  Trustee  or such  Holder  of  Debentures,  as
applicable,  has actual  knowledge  that such payment is  prohibited  by Section
14.1(a) or (b) hereof,  such payment shall be held by the Trustee or such Holder
of Debentures in trust for the benefit of, and shall be paid  forthwith over and
delivered  upon written  request to, the holders of Senior  Indebtedness  of the
Company,   as  their   interests  may  appear,   or  their  agent,   trustee  or
representative (a  "Representative")  under the indenture or other agreement (if
any) pursuant to which Senior  Indebtedness of the Company may have been issued,
as their respective  interests may appear, for application to the payment of all
obligations with respect to Senior  Indebtedness of the Company remaining unpaid
to the extent necessary to pay such obligations in full in accordance with their
terms,  after giving effect to any concurrent  payment or distribution to or for
the holders of Senior Indebtedness of the Company.

         With respect to the holders of Senior Indebtedness of the Company,  the
Trustee  undertakes to perform only such  obligations on the part of the Trustee
as are  specifically  set forth in this  Article,  and no implied  covenants  or
obligations  with respect to the holders of Senior  Indebtedness  of the Company
shall be read into this Indenture against the Trustee.  The Trustee shall not be
deemed to owe any fiduciary  duty to the holders of Senior  Indebtedness  of the
Company,  and shall not be liable to any such  holders if the Trustee  shall pay
over or  distribute  to or on behalf of Holders of  Debentures or the Company or
any other Person money or assets to which any holders of Senior  Indebtedness of
the Company shall be entitled by virtue of this Article,  except if such payment
is made as a  result  of the  willful  misconduct  or  gross  negligence  of the
Trustee.

                                      -10-
<PAGE>

         14.3. Notice By Company.  The Company shall promptly notify the Trustee
of any facts known to the Company that would cause a payment of any  Obligations
to violate  this  Article,  but failure to give such notice shall not affect the
subordination  of the  Debentures to the Senior  Indebtedness  of the Company as
provided in this Article.

         14.4.  Subrogation.  After  all  obligations  with  respect  to  Senior
Indebtedness  of the Company are paid in full, and until the Debentures are paid
in full,  Holders of Debentures  shall be subrogated to the rights of holders of
Senior Indebtedness of the Company to receive distributions applicable to Senior
Indebtedness of the Company to the extent that  distributions  otherwise payable
to the  Holders  of  Debentures  have  been  applied  to the  payment  of Senior
Indebtedness of the Company.  A distribution  made under this Article to holders
of Senior  Indebtedness  of the Company that  otherwise  would have been made to
Holders of Debentures is not, as between the Company and Holders of  Debentures,
a payment by the Company on the Securities.

         14.5.  Relative  Rights.  This Article  defines the relative  rights of
Holders of Debentures and holders of Senior Indebtedness of the Company. Nothing
in this Indenture shall:

                  (1) impair,  as between the Company and Holders of Debentures,
         the obligation of the Company, which is absolute and unconditional,  to
         pay  principal of and interest on the  Debentures  in  accordance  with
         their terms;

                  (2) affect the relative  rights of Holders of  Debentures  and
         creditors of the Company other than their rights in relation to holders
         of Senior Indebtedness of the Company; or

                  (3)  prevent  the  Trustee  or any Holder of  Debentures  from
         exercising its available remedies upon an Event of Default,  subject to
         the rights of holders and owners of Senior  Indebtedness of the Company
         to receive  distributions and payments  otherwise payable to Holders of
         Debentures.

         If the Company  fails  because of this  Article to pay  principal of or
interest on a Debenture on the due date,  unless  during an Extension  Period in
accordance  with  Section 4.1 of  Supplemental  Indenture  No. 1, the failure is
still an Event of Default.

         14.6.  Subordination  May Not Be Impaired  by Company.  No right of any
holder of Senior Indebtedness of the Company to enforce the subordination of the
Debentures  shall be impaired by any act or failure to act by the Company or any
Holder  of  Debentures  or by the  failure  of the  Company  or  any  Holder  of
Debentures to comply with this Indenture.

         14.7. Distribution or Notice to Representative. Whenever a distribution
is to be made or a  notice  given  to  holders  of  Senior  Indebtedness  of the
Company,   the   distribution  may  be  made  and  the  notice  given  to  their
Representative.

         Upon any payment or distribution  of assets of the Company  referred to
in this Article,  the Trustee and the Holders of Debentures shall be entitled to
rely upon any order or decree  made by any court of  competent  jurisdiction  or
upon any certificate of such  Representative  or of the  liquidating  trustee or
agent or other Person making any  distribution  to the Trustee or to the

                                      -11-
<PAGE>

holders for the purpose of ascertaining  the Persons  entitled to participate in
such  distribution,  the holders of the Senior  Indebtedness  of the Company and
other  indebtedness  of the  Company,  the amount or amounts  thereof or payable
thereon,  the amount or amounts paid or distributed  thereon and all other facts
pertinent thereto or to this Article.

         14.8.  Authorization  of Trustee  to  Effectuate  Subordination  of the
Debentures. Each Holder of Debentures, by its acceptance thereof, authorizes and
expressly  directs  the  Trustee  on its  behalf to take  such  action as may be
necessary  or  appropriate  to  effectuate,  as  between  the  Holders  of  such
Debentures  and  the  holders  of  Senior  Indebtedness  of  the  Company,   the
subordination  provided in this Article,  and appoints the Trustee to act as the
Holders' of Debentures attorney-in-fact for any and all such purposes.

                                  ARTICLE VIII
                                  EFFECTIVENESS

         This  Supplemental  Indenture shall be effective for all purposes as of
the date and time this Supplemental Indenture has been executed and delivered by
the  Company  and the  Trustee  in  accordance  with  Article  Nine of the  Base
Indenture.  As supplemented  hereby,  the Base Indenture is hereby  confirmed as
being in full force and effect.

                                   ARTICLE IX
                                  MISCELLANEOUS

         9.1.  Separability.  In the event any  provisions of this  Supplemental
Indenture  shall be held  invalid  or  unenforceable  by any court of  competent
jurisdiction,  such holding  shall not  invalidate or render  unenforceable  any
other provision hereof or any provision of the Indenture.

         9.2.  Supplemental  Indenture Controls. To the extent that any terms of
this Supplemental  Indenture or the Notes are inconsistent with the terms of the
Indenture,  the terms of this  Supplemental  Indenture or the Notes shall govern
and supersede such inconsistent terms.

         9.3.  Governing Law. This  Supplemental  Indenture shall be governed by
and construed in accordance with the law of the State of New York.

         9.4.  Counterparts.  This  Supplemental  Indenture  may be  executed in
several counterparts,  each of which shall be an original and all of which shall
constitute but one and the same instrument.


                                      -12-
<PAGE>


         IN WITNESS  WHEREOF,  the  Company  and the  Trustee  have  caused this
Supplemental  Indenture  to be  executed  as an  instrument  under seal in their
respective corporate names as of the date first above written.

                              SENIOR HOUSING PROPERTIES TRUST


                              By:___________________________
                                    Name:
                                    Title:


                              STATE STREET BANK AND TRUST COMPANY, as Trustee


                              By:___________________________
                                    Name:
                                    Title:

                                      -13-
<PAGE>
                                    EXHIBIT A

                 [FORM OF FACE OF JUNIOR SUBORDINATED DEBENTURE]

               10.125% Junior Subordinated Notes due June 15, 2041

                         SENIOR HOUSING PROPERTIES TRUST

No. ___                                                              $ ___

         Senior Housing  Properties  Trust, a real estate  investment trust duly
organized and existing under the laws of Maryland  (herein called the "Company",
which  term  includes  any  successor  Person  under the  Indenture  hereinafter
referred   to),   for   value    received,    hereby    promises   to   pay   to
 ..................................., or registered assigns, the principal sum of
 ..................... Dollars on June 15, 2041.

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

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

                              SENIOR HOUSING PROPERTIES TRUST


                              By:_____________________________
                                    Name:
                                    Title:

Dated: _______

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

STATE STREET BANK AND TRUST COMPANY,
as Trustee

By:__________________________________
      Name:
      Title:


<PAGE>
             [FORM OF REVERSE OF THE JUNIOR SUBORDINATED DEBENTURE]


                         SENIOR HOUSING PROPERTIES TRUST

            10.125% Junior Subordinated Debentures due June 15, 2041

         Capitalized terms used herein have the meanings assigned to them in the
Indenture (as defined below) unless otherwise indicated.

         1.  Indenture.  The  Company  issued its  10.125%  Junior  Subordinated
Debentures due June 15, 2041 (the "Debentures") as part of a series issued under
a Junior  Subordinated  Indenture  dated as of June 21, 2001 and a  Supplemental
Indenture No. 1 dated as of June 21, 2001  (collectively,  the "Indenture") each
between the Company and State  Street Bank and Trust  Company,  as Trustee  (the
"Trustee").  The terms of the  Debentures  include those stated in the Indenture
and those made a part of the  Indenture by reference to the Trust  Indenture Act
of 1939 as in effect on the date of the Indenture. The Debentures are subject to
all such terms,  and the Holders of the Debentures are referred to the Indenture
and the Trust Indenture Act of 1939 for a statement of such terms.  The terms of
the  Indenture  shall govern any  inconsistencies  between the Indenture and the
Debentures. The Debentures are unsecured subordinated general obligations of the
Company. The Debentures issued pursuant to said Supplemental Indenture No. 1 are
in the initial aggregate  principal amount of up to $29,639,200,  subject to the
right of the  Company  set forth in the  Indenture  to reopen the  series  which
comprises the Debentures.

         2. Interest.  Senior Housing  Properties  Trust, a Maryland real estate
investment (the "Company")  promises to pay interest on the principal  amount of
this Debenture at the rate and in the manner specified below.

         This Debenture will bear interest at the rate of 10.125% per annum (the
"Coupon  Rate") from and  including  June 21, 2001 until the  principal  thereof
becomes due and payable,  and will bear interest on any overdue principal at the
Coupon Rate and (to the extent  that  payment of such  interest  is  enforceable
under applicable law) on any overdue  installment of interest at the Coupon Rate
("Additional  Interest") until paid, compounded  quarterly,  payable (subject to
the  provisions  of the  Indenture)  quarterly  in  arrears  on the  15th day of
September,  December,  March and June of each year (each,  an "Interest  Payment
Date"),  commencing  on  September  15,  2001 to the  Person in whose  name such
Debenture  is  registered  at the  close of  business  on the  Record  Date next
preceding such Interest Payment Date.

         The  "Record  Date" for payment of interest  will be one  Business  Day
before the Interest  Payment  Date,  unless such  Debenture is  registered  to a
holder other than the Property Trustee or a nominee of the Depositary,  in which
case the Record Date for payment of interest will be the fifteenth  calendar day
before the  applicable  Interest  Payment  Date,  whether or not a Business Day.
Until liquidation, if any, of the Trust, the Debentures will be held in the name
of the  Property  Trustee in trust for the  benefit of the  holders of the Trust
Securities.

         The amount of  interest  payable for any period will be computed on the
basis of a 360-day year of twelve 30-day  months.  In the event that any date on
which  interest is payable on the

                                      A-2
<PAGE>

Debentures is not a Business Day, then payment of interest  payable on such date
will be made on the next succeeding day which is a Business Day (and without any
interest or other payment in respect of any such delay), with the same force and
effect as if made on the date such payment was originally payable.

         THE INDEBTEDNESS OF THE COMPANY EVIDENCED BY THIS DEBENTURE,  INCLUDING
THE PRINCIPAL  HEREOF AND INTEREST  HEREON,  IS, TO THE EXTENT AND IN THE MANNER
SET FORTH IN THE  INDENTURE,  SUBORDINATE  AND JUNIOR IN RIGHT OF PAYMENT TO THE
PRIOR PAYMENT IN FULL IN CASH OR OTHER PERMITTED  CONSIDERATION OF THE COMPANY'S
OBLIGATIONS  TO HOLDERS OF SENIOR  INDEBTEDNESS  OF THE COMPANY.  EACH HOLDER OF
THIS DEBENTURE,  BY ACCEPTANCE  HEREOF, (A) AGREES TO AND SHALL BE BOUND BY SUCH
PROVISIONS  OF THE  INDENTURE AND ALL OTHER  PROVISIONS  OF THE  INDENTURE,  (B)
AUTHORIZES  AND  DIRECTS THE TRUSTEE ON HIS BEHALF TO TAKE SUCH ACTION 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.

         3. Extension of Interest Payment Period. So long as no Event of Default
under the Indenture has occurred and is  continuing,  the Company shall have the
right, at any time during the term of the Debentures, from time to time to defer
the payment of interest and  Additional  Sums, if any, by extending the interest
payment  period of such  Debenture  for a period not  exceeding  20  consecutive
quarters (an "Extension  Period").  No Extension  Period shall extend beyond the
Stated  Maturity of the Debentures.  To the extent  permitted by applicable law,
accrued and unpaid  interest and Additional  Sums, the payment of which has been
deferred because of an Extension Period imposed pursuant to the Indenture,  will
bear  Additional  Interest  compounded  quarterly.  At the end of the  Extension
Period,  the  Company  shall pay all  interest  then  accrued  and unpaid on the
Debentures,   including  any  Additional   Interest  and  Additional   Sums,  if
applicable,  to the holders of the  Debentures in whose names the Debentures are
registered  in the  Register on the first Record Date  preceding  the end of the
Extension Period.

         Before the termination of any Extension  Period,  the Company may elect
to (i) shorten  the  Extension  Period or (ii)  further  extend  such  Extension
Period,  provided  that such period  together  with all such further  extensions
thereof shall not exceed 20  consecutive  quarters,  or extend beyond the Stated
Maturity. At any time following the termination of any Extension Period and upon
the payment of any accrued and unpaid  Additional  Interest and Additional Sums,
if applicable,  then due, the Company may elect to begin a new Extension Period,
subject to the foregoing  requirements.  No interest or Additional Sums shall be
due and payable during an Extension Period, except at the end thereof.

         Subject to certain  exceptions set forth in the  Indenture,  during any
such Extension Period, the Company shall not (i) declare or pay any dividends or
distributions  on, or redeem,  purchase,  acquire or make a liquidation  payment
with respect to, any of the Company's shares of beneficial  interest,  (ii) make
any  payment of  principal  of or interest  or  premium,  if any,  on, or repay,
repurchase  or redeem any  indebtedness  or debt  securities of the Company that
rank on a parity with or junior to the  Debentures  in right of payment or (iii)
make any  guarantee  payments  with  respect to any  guarantee by the Company of
indebtedness  or  debt  securities  of any  Subsidiary  of

                                      A-3
<PAGE>

the Company if such  guarantee  ranks on parity with or junior to the Debentures
in right of payment.

         The  Company  shall give notice of its  election  to begin,  shorten or
extend an Extension Period as provided in the Indenture.

         4. Tax Event of Investment Company Event Redemption.  If a Tax Event or
Investment  Company  Event  (either  a  "Special  Event")  shall  occur  and  be
continuing,  the  Company may redeem the  Debenture  at any time within 180 days
following the occurrence of that Special  Event,  in whole but not in part, at a
redemption  price equal to 100% of the principal  amount of the Debentures  plus
accrued and unpaid interest thereon to the Redemption Date.

         5. Optional Redemption. The Company shall have the option to redeem the
Debentures  at any time on or after  June 15,  2006,  in whole or in part,  at a
redemption  price equal to 100% of the principal  amount of the Debentures  plus
accrued and unpaid interest thereon to the Redemption Date.

         6.  Denominations,   Transfer  and  Exchange.  The  Debentures  may  be
transferred  or  exchanged  only in minimum  denominations  of $25 and  integral
multiples of $25 in excess thereof,  and any attempted  transfer,  sale or other
disposition of Debentures in a denomination  of less than $25 shall be deemed to
be void and of no legal  effect  whatsoever,  and any such  transferee  shall be
deemed not to be the holder of such  Debentures  for any purpose,  including but
not limited to the receipt of  payments in respect of such  Debentures  and such
transferee shall be deemed to have no interest whatsoever in such Debentures.

         7.   Authentication.   This   Debenture   shall  not  be  valid   until
authenticated by the manual signature of the Trustee or an authenticating agent.

         8. Persons Deemed Owners.  The Company,  the Trustee,  and any agent of
the  Company  or  Trustee  may deem  and  treat  the  Person  in whose  name the
Debentures  are  registered  as the  absolute  owner for  purposes of  receiving
payment of principal and interest.

         9.  Defaults  and  Remedies.  In the case of an Event of  Default  with
respect to the Debentures  shall have occurred and be continuing,  the principal
hereof may be declared, and upon such declaration shall become, due and payable,
in the manner, with the effect and subject to the provisions provided for in the
Indenture.

         10. Actions of Holders.  The Indenture contains  provisions  permitting
the holders of not less than a majority in principal  amount of the  Debentures,
subject to certain  provisions  and exceptions as provided for in the Indenture,
to (a) waive  certain  past Events of Defaults  and their  consequences  and (b)
direct the time,  method and place of conducting  any  proceeding for any remedy
available  to the Trustee or for  exercising  any trust power  conferred  on the
Trustee.

         11.  Governing Law. This Debenture  shall be governed by, and construed
in accordance with, the laws of the State of New York.

         12. No Personal  Liability.  THE ARTICLES OF AMENDMENT AND  RESTATEMENT
ESTABLISHING SENIOR HOUSING PROPERTIES TRUST DATED

                                      A-4
<PAGE>

SEPTEMBER 20, 1999, A COPY OF WHICH,  TOGETHER WITH ALL AMENDMENTS  THERETO (THE
"DECLARATION"), IS DULY FILED IN THE OFFICE OF THE DEPARTMENT OF ASSESSMENTS AND
TAXATION  OF THE  STATE OF  MARYLAND,  PROVIDES  THAT THE NAME  "SENIOR  HOUSING
PROPERTIES  TRUST" REFERS TO THE TRUSTEES UNDER THE DECLARATION  COLLECTIVELY AS
TRUSTEES,  BUT NOT  INDIVIDUALLY  OR PERSONALLY,  AND THAT NO TRUSTEE,  OFFICER,
SHAREHOLDER,  EMPLOYEE  OR AGENT OF THE  COMPANY  SHALL BE HELD TO ANY  PERSONAL
LIABILITY,  JOINTLY OR SEVERALLY,  FOR ANY OBLIGATION OF, OR CLAIM AGAINST,  THE
COMPANY.  ALL PERSONS  DEALING WITH THE COMPANY,  IN ANY WAY, SHALL LOOK ONLY TO
THE ASSETS OF THE COMPANY FOR THE PAYMENT OF ANY SUM OR THE  PERFORMANCE  OF ANY
OBLIGATION.







                                      A-5
<PAGE>




         FOR VALUE RECEIVED, the undersigned hereby sell(s) and transfer(s) unto

_______________________________________________________________________________.
     (please insert Social Security or other identifying number of assignee)


_______________________________________________________________________________.

_______________________________________________________________________________.


_______________________________________________________________________________.
PLEASE  PRINT  OR  TYPEWRITE  NAME AND  ADDRESS,  INCLUDING  POSTAL  ZIP CODE OF
ASSIGNEE

the within Debenture and all rights thereunder,  hereby irrevocably constituting
and appointing

_______________________________________________________________________________.

_______________________________________________________________________________.

_______________________________________________________________________________.


_______________________________________________________________________________.

_______________________________________________________________________________.

_______________________________________________________________________________.
agent to transfer said Debenture on the books of the Company, with full power of
substitution in the premises.


Dated: __________________ __, ____



                                    ________________________

NOTICE:  The  signature  to this  assignment  must  correspond  with the name as
written  upon the face of the  within  instrument  in every  particular  without
alteration or enlargement, or any change whatever.


                                      A-6