SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person* Lyons Mark Donald (Last) (First) (Middle) ONE LIBERTY PLAZA, 53RD FLOOR (Street) NEW YORK NY 10006 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 05/03/2006	3. Issuer Name and Ticker or Trading Symbol ARCH CAPITAL GROUP LTD. [ ACGL ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director 10% Owner X Officer (give title below) Other (specify below) COO Insur Gr. Operations	5. If Amendment, Date of Original Filed (Month/Day/Year)
			6. Individual or Joint/Group Filing (Check Applicable Line) X Form filed by One Reporting Person Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Shares, $.01 par value per share	32,023(1)	D

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock Option (right to buy)	(2)	08/06/2012	Common Shares, $.01 par value per share	18,116	$26.31	D
Stock Option (right to buy)	(3)	09/22/2014	Common Shares, $.01 par value per share	28,000	$39	D
Stock Option (right to buy)	(4)	02/23/2016	Common Shares, $.01 par value per share	20,000	$56.27	D

Explanation of Responses:

1. 962 of such shares are restricted and subject to vest on February 26, 2007; 1,666 of such shares are restricted and subject to vest on September 22, 2006 and 3,000 of such shares are restricted and subject to vest in three equal annual installments commencing on February 23, 2007.

2. The stock options became exerciable in three equal annual installments commencing on August 6, 2002.

3. The stock options became exerciable in three equal annual installments commencing on September 22, 2004.

4. The stock option will become exercisable in three equal installments, with the first installment becoming exercisable on February 23, 2007 and the next two installments on February 23, 2008 and February 23, 2009.

	/s/ Mark D. Lyons	05/05/2006
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 5 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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