SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13D/A
                                 (Rule 13d-101)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
             TO RULE 13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT
                                TO RULE 13d-2(a)
                               (Amendment No. 8)*

                         SENIOR HOUSING PROPERTIES TRUST
                                (Name of Issuer)

              COMMON SHARES OF BENEFICIAL INTEREST, $0.01 PAR VALUE
                         (Title of Class of Securities)

                                   81721M 10 9
                                 (CUSIP Number)

                                 John A. Mannix
                              HRPT Properties Trust
                                400 Centre Street
                                Newton, MA 02458
                                 (617) 332-3990
           (Name, Address and Telephone Number of Person Authorized to
                      Receive Notices and Communications)

                                December 17, 2004
             (Date of Event which Requires Filing of this Statement)




If the filing person has previously  filed a statement on Schedule 13G to report
the  acquisition  that is the subject of this  Schedule  13D, and is filing this
schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box
|_|.

Note:  Schedules  filed in paper format shall include a signed original and five
copies of the  schedule,  including  all  exhibits.  See Rule 13d-7(b) for other
parties to whom copies are to be sent.

                         (Continued on following pages)

                               (Page 1 of 9 Pages)
_________________________

* The remainder of this cover page shall be filled out for a reporting  person's
initial filing on this form with respect to the subject class of securities, and
for  any  subsequent   amendment   containing   information  which  would  alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the  Securities  Exchange  Act of
1934 ("Act") or otherwise  subject to the liabilities of that section of the Act
but  shall be  subject  to all other  provisions  of the Act  (however,  see the
Notes).

                                  SCHEDULE 13D

CUSIP NO. 81721M 10 9                                          Page 2 of 9 Pages


1            NAMES OF REPORTING PERSONS
             I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

             HRPT Properties Trust  I.R.S. ID No. 04-6558834

2            CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*      (a) |_|
                                                                    (b) |_|


3            SEC USE ONLY


4            SOURCE OF FUNDS*

             WC

5            CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
             TO ITEMS 2(d) OR 2(e)     |_|


6            CITIZENSHIP OR PLACE OF ORGANIZATION

             Maryland

                              7            SOLE VOTING POWER
         NUMBER OF
          SHARES                           8,660,738
       BENEFICIALLY
         OWNED BY             8            SHARED VOTING POWER                  
           EACH                                                                 
         REPORTING                                                              
          PERSON              9            SOLE DISPOSITIVE POWER               
           WITH                                                                 
                                           8,660,738                            
                                                                                
                              10           SHARED DISPOSITIVE POWER             


11           AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

             8,820,517

12           CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN 
             SHARES*                          |_|


13           PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

             12.9%

14           TYPE OF REPORTING PERSON*

             OO

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!





                                  SCHEDULE 13D


CUSIP NO. 81721M 10 9                                          Page 3 of 9 Pages


1            NAMES OF REPORTING PERSONS
             I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

             Reit Management & Research LLC  I.R.S. ID No. 04-3583787

2            CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*        (a) |_|
                                                                      (b) |_|

3            SEC USE ONLY


4            SOURCE OF FUNDS*

             OO

5            CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
             TO ITEMS 2(d) OR 2(e)     |_|


6            CITIZENSHIP OR PLACE OF ORGANIZATION

             Delaware

                              7            SOLE VOTING POWER
         NUMBER OF
          SHARES
       BENEFICIALLY           8            SHARED VOTING POWER                  
         OWNED BY                                                               
           EACH                                                                 
         REPORTING            9            SOLE DISPOSITIVE POWER               
          PERSON                                                                
           WITH                                                                 
                              10           SHARED DISPOSITIVE POWER             
                                                                                
                                                                                
11           AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

             8,870,484

12           CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
             SHARES*                          |_|


13           PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

             13.0%

14           TYPE OF REPORTING PERSON*

             OO

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!





                                  SCHEDULE 13D


CUSIP NO. 81721M 10 9                                          Page 4 of 9 Pages


1            NAMES OF REPORTING PERSONS
             I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

             Reit Management & Research Trust  I.R.S. ID No. 04-3402206

2            CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*        (a) |_|
                                                                      (b) |_|

3            SEC USE ONLY


4            SOURCE OF FUNDS*

             OO

5            CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT 
             TO ITEMS 2(d) OR 2(e)     |_|


6            CITIZENSHIP OR PLACE OF ORGANIZATION

             Massachusetts

                              7            SOLE VOTING POWER
         NUMBER OF
          SHARES
       BENEFICIALLY           8            SHARED VOTING POWER                  
         OWNED BY                                                               
           EACH                                                                 
         REPORTING            9            SOLE DISPOSITIVE POWER               
          PERSON                                                                
           WITH                                                                 
                              10           SHARED DISPOSITIVE POWER             
                                                                                
                                                                                
11           AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

             8,870,484

12           CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
             SHARES*                          |_|


13           PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

             13.0%

14           TYPE OF REPORTING PERSON*

             OO

                      *SEE INSTRUCTIONS BEFORE FILLING OUT!



                                  SCHEDULE 13D

CUSIP NO. 81721M 10 9                                          Page 5 of 9 Pages


         This Amendment No. 8 to the original Schedule 13D filed September 29,
1999, by HRPT Properties Trust and Reit Management & Research, Inc. and the
original Schedule 13D filed October 23, 2001, by Reit Management & Research
Trust is being filed to reflect the closing of the sale of 1,000,000 Common
Shares of Beneficial Interest, par value $0.01, of Senior Housing Properties
Trust owned by HRPT Properties Trust in an underwritten public offering at a
purchase price per share of $19.86 (the "HRP Sale") and the grant by HRPT
Properties Trust to the underwriters of that transaction, the option to purchase
up to an additional 900,000 Shares (defined below) at a purchase price per share
of $19.86 on or prior to January 13, 2005 to cover over-allotments, if any (the
"Over-Allotment Option"), and to update certain other information.

Item 1.  Security and Issuer.

         The class of equity securities to which this statement relates is the
Common Shares of Beneficial Interest, par value $0.01 (the "Shares"), of Senior
Housing Properties Trust, a Maryland real estate investment trust ("SNH"), with
its principal executive offices located at 400 Centre Street, Newton,
Massachusetts 02458.

Item 2.  Identity and Background.

         The persons filing this statement are HRPT Properties Trust, a Maryland
real estate investment trust ("HRP"), Reit Management & Research LLC, a Delaware
limited liability company ("RMR"), and Reit Management & Research Trust, a
Massachusetts business trust ("RMR Trust").

         HRP's principal business is to operate as a real estate investment
trust. The principal office of HRP is located at 400 Centre Street, Newton,
Massachusetts 02458. The trustees of HRP are Tjarda Clagett, Patrick F. Donelan,
Gerard M. Martin, Barry M. Portnoy and Frederick N. Zeytoonjian. The executive
officers of HRP are John A. Mannix, President and Chief Operating Officer, John
C. Popeo, Treasurer, Chief Financial Officer and Secretary, Adam D. Portnoy,
Executive Vice President, Jennifer B. Clark, Senior Vice President, and David M.
Lepore, Senior Vice President.

         RMR's principal business is providing advisory services to real estate
investment trusts such as SNH and others. The principal office of RMR is located
at 400 Centre Street, Newton, Massachusetts 02458. The directors of RMR are
David J. Hegarty, Gerard M. Martin and Barry M. Portnoy. The executive officers
of RMR are David J. Hegarty, President and Secretary, John G. Murray, Executive
Vice President, Evrett W. Benton, Vice President, Jennifer B. Clark, Vice
President, David M. Lepore, Vice President, John A. Mannix, Vice President,
Thomas M. O'Brien, Vice President, John C. Popeo, Vice President and Treasurer,
John R. Hoadley, Vice President, Bruce J. Mackey Jr., Vice President, Mark L.
Kleifges, Vice President, Ethan S. 



                                  SCHEDULE 13D

CUSIP NO. 81721M 10 9                                          Page 6 of 9 Pages


Bornstein, Vice President and Adam D. Portnoy, Vice President. The sole member
and manager of RMR is RMR Trust.

         RMR Trust's principal business is to act as the member and manager of
RMR. The principal office of RMR Trust is located at 400 Centre Street, Newton,
Massachusetts 02458. The trustees and executive officers of RMR Trust are the
same as the directors and executive officers of RMR. Each of Messrs. Martin and
Portnoy own 50% of the outstanding capital stock of RMR Trust.

         Each of the individuals listed above (i) has a business address at 400
Centre Street, Newton, Massachusetts 02458, (ii) except for Mr. Donelan, is a
United States citizen and (iii) except for Messrs. Clagett, Donelan and
Zeytoonjian is principally employed by RMR in the capacities specified above.
Mr. Hegarty also serves as the President, Chief Operating Officer and Secretary
of SNH, and Mr. Hoadley also serves as Treasurer and Chief Financial Officer of
SNH. The principal office of SNH is located at 400 Centre Street, Newton,
Massachusetts 02458. Mr. Clagett is principally employed as a private investor.
Mr. Donelan is principally employed as a private investor. Mr. Zeytoonjian is
Chairman and Chief Executive Officer of Turf Products Corporation and is also a
trustee of SNH.

         Neither HRP, RMR, RMR Trust nor any of the individuals specified above
has, during the last five years, been convicted in a criminal proceeding
(excluding traffic violations or similar misdemeanors), or been party to any
civil proceeding which resulted in a judgment, decree or final order enjoining
future violations of, or prohibiting or mandating activities subject to, federal
or state securities laws or finding any violation with respect to such laws.

Item 5.  Interest in Securities of the Issuer.

         (a) Giving effect to the HRP Sale, HRP holds 8,660,738 Shares, which
represent 12.6% of the issued and outstanding Shares.

         In addition, the trustees and executive officers of HRP own SNH Shares
as follows: Mr. Martin, through a corporation of which Mr. Martin is the sole
stockholder, 68,989 Shares; Mr. Portnoy, through a corporation of which Mr.
Portnoy is the sole stockholder, 68,990 Shares; and other trustees and executive
officers of HRP, 21,800 Shares in the aggregate. In addition, Messrs. Portnoy
and Martin, as Managing Trustees of HRP, may be deemed to have beneficial
ownership of the 8,660,738 Shares held by HRP; however, Messrs. Portnoy and
Martin disclaim beneficial ownership of HRP's 8,660,738 Shares. The Shares held
by HRP, when aggregated with such additional Shares held by the trustees and
executive officers of HRP, aggregate 8,820,517 Shares, which represent 12.9% of
the issued and outstanding Shares. The Shares held by Mr. Martin, Mr. Portnoy
and the other trustees and executive officers of HRP are reported herein
pursuant to the provisions of Items 2 and 5 of Schedule 13D. HRP, however,
expressly disclaims any 



                                  SCHEDULE 13D

CUSIP NO. 81721M 10 9                                          Page 7 of 9 Pages


beneficial ownership of the Shares held by Mr. Martin, Mr. Portnoy and the other
trustees and executive officers of HRP.

         RMR, as HRP's investment manager, and RMR Trust, as the sole member and
manager of RMR, may under applicable regulatory definitions, be deemed to
beneficially own HRP's 8,660,738 Shares. RMR and RMR Trust, however, expressly
disclaim any beneficial ownership of HRP's 8,660,738 Shares.

            In addition, the trustees, directors and executive officers of RMR
and RMR Trust own SNH Shares as follows, in part as noted above: Mr. Martin,
through a corporation of which Mr. Martin is the sole stockholder, 68,989
Shares; Mr. Portnoy, through a corporation of which Mr. Portnoy is the sole
stockholder, 68,990 Shares; Mr. Hegarty, 19,670 Shares; and other executive
officers of RMR Trust, 52,097 Shares in the aggregate. The Shares held by HRP
(which may be deemed to be beneficially owned by RMR and RMR Trust), when
aggregated with such additional Shares held by the trustees and executive
officers of RMR Trust, aggregate 8,870,484 Shares, which represent 13.0% of the
issued and outstanding Shares. The Shares held by Mr. Martin, Mr. Portnoy, Mr.
Hegarty and the other executive officers of RMR and RMR Trust are reported
herein pursuant to the provisions of Items 2 and 5 of Schedule 13D. RMR and RMR
Trust, however, expressly disclaim any beneficial ownership of the Shares held
by Mr. Martin, Mr. Portnoy, Mr. Hegarty and the other executive officers of RMR
and RMR Trust.

         (b) HRP has sole power to vote or dispose of its 8,660,738 Shares. To
HRP's knowledge, each of the trustees, directors and executive officers of HRP,
RMR and RMR Trust described above has sole power to vote or dispose of the
Shares he or she beneficially owns.

         (c) Other than the HRP Sale, no transactions in Shares have been
effected during the past sixty days by HRP, RMR, RMR Trust or the trustees,
directors and executive officers of HRP, RMR and RMR Trust described above.

         (d) No other person is known to have the right to receive or the power
to direct the receipt of distributions from, or the proceeds from the sale of
securities covered by this statement.

Item 6.  Contracts, Arrangements, Understandings or Relationships With Respect
         to Securities of the Issuer.

         Other than the potential transaction contemplated by the Over-Allotment
Option, HRP has formed no definitive intent to sell the Shares or any portion
thereof. However, depending upon its continuing review of its investments and
various other facts, HRP may in the future desire, subject to any applicable
securities laws, to sell all or a portion of the Shares. SNH has registered the
offer and sale of the Shares under the Securities Act of 1933, as amended (the



                                  SCHEDULE 13D

CUSIP NO. 81721M 10 9                                          Page 8 of 9 Pages


"Securities Act"), pursuant to a registration statement on Form S-3 (No.
333-109659). That registration statement became effective on October 24, 2003.
In connection with the registration statement, HRP and SNH entered into a
Registration Agreement (the "Registration Agreement"). Under the Registration
Agreement, SNH agreed to, among other things, file the registration statement
and use reasonable efforts to effect the registration of the Shares and HRP,
among other things, agreed to pay all expenses incurred by SNH relating to the
registration and any sale of the Shares. SNH also agreed to indemnify HRP
against certain liabilities, including liabilities under the Securities Act and,
alternately, to contribute to payments that HRP may be required to make as a
result of these liabilities.

         The HRP Sale was consummated pursuant to an Underwriting Agreement,
dated December 14, 2004, between SNH, HRP, and the underwriters named therein
(the "Underwriting Agreement"). Pursuant to the Underwriting Agreement, SNH
issued and sold, concurrently with the HRP Sale, 5,000,000 Shares in an
underwritten public offering at a purchase price per share of $19.86. The
Underwriting Agreement also provides that total expenses of the offering,
including underwriting discounts and commissions, will be paid by SNH and HRP
pro-rata to the number of Shares sold by SNH and HRP, respectively, including
shares sold by HRP pursuant to the Over-Allotment Option, if any.

Item 7.  Material to be Filed as Exhibits.

         The following document is filed as an exhibit to this statement:

         99.1     Underwriting Agreement, dated December 14, 2004, between
                  Senior Housing Properties Trust, HRPT Properties Trust, and
                  the underwriters named therein (incorporated by reference to
                  Exhibit 1.1 to SNH's Current Report on Form 8-K dated December
                  14, 2004).





                                    SIGNATURE

         After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


December 21, 2004                         HRPT PROPERTIES TRUST


                                          By: /s/ John C. Popeo
                                              John C. Popeo
                                              Treasurer, Chief Financial Officer
                                              and Secretary 



                                          REIT MANAGEMENT & RESEARCH LLC


                                          By: /s/ John C. Popeo
                                              John C. Popeo
                                              Vice President and Treasurer


                                          REIT MANAGEMENT & RESEARCH TRUST


                                          By: /s/ John C. Popeo
                                              John C. Popeo
                                              Vice President and Treasurer