Arch Capital Group Ltd. A Bermuda-based company, announced yesterday that it has entered into a definitive agreement to acquire Rock River Insurance Company, an approved excess and surplus lines insurer in 45 states and the District of Columbia and an admitted insurer in two other states.

Under the terms of the agreement, the existing policies and other liabilities of Rock River will be reinsured or otherwise assumed by seller, Sentry Insurancewhich has an AM Best rating of A+.

The transaction is contingent on obtaining applicable regulatory approvals and other customary closing conditions.

The acquisition of Rock River will provide Arch Risk Transfer Services ("ART Services"), Arch Capital's recently acquired insurance program and alternative market business, with the capability of writing excess and surplus lines business.

The ART Services group of companiesincludes First American Insurance Company, an admitted insurer with licenses in 49 states.