ST. LOUIS (

TheStreet

) --

Stifel Financial

(SF) - Get Report

has agreed to buy its investment bank rival

Thomas Weisel Partners

( TWPG) for more than $300 million.

Each Thomas Weisel share will be exchanged for 0.1364 a common share of Stifel.

Thomas Weisel shares are valued at $7.60, a premium of more than 74% to their closing price of $4.36 on Friday based on Stifel's closing price Friday of $55.74.

Estimated annual revenue for the combined company would be about $1.6 billion, with a pro forma market capitalization of about $2 billion, the companies said Monday.

The merger is expected to close around June 30.

-- Reported by Joseph Woelfel in New York.

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