13G Filing: Arrowstreet Capital and Atwood Oceanics Inc (NYSE:ATW)

Item 3.

If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

[_]     Broker or dealer registered under Section 15 of the Act;

[_]     Bank as defined in Section 3(a)(6) of the Act;

[_]     Insurance company as defined in Section 3(a)(19) of the Act;

[_]     Investment company registered under Section 8 of the Investment Company Act of 1940;

[X]     An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E);

[_]     An employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F);

[X]     A parent holding company or control person in accordance with Rule 13d-1(b)(1)(ii)(G);

[_]     A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

[_]     A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940;

[_]     A non-U.S. institution in accordance with Rule 240.13d-1(b)(1)(ii)(J);

[_]     Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K). If filing as a non-U.S. institution in accordance with Rule 240.13d-1(b)(1)(ii)(J),

          please specify the type of institution: ____

Ownership

(a)

Amount Beneficially Owned:

3,171,226

ASC:    3.9%

ACH:   3.9%

(iii)  Sole power to  dispose or to direct the disposition of: