Baltimore-based regional bank Mercantile Bankshares ( MRBK) agreed to acquire James Monroe Bancorp ( JMBI) for about $142.9 million in stock and cash. James Monroe shareholders will receive $23.50 in cash or 0.6033 shares of Mercantile Bankshares for each share they hold. The cash price represents a 27% premium over James Monroe's Friday closing price of $18.54. The offer is valid as long as 50% to 66% of the total consideration is paid in stock, the companies said. The deal is expected to be completed in the third quarter, pending shareholder and regulatory approval. The acquisition would add $530 million in assets to Mercantile, which currently has about $16 billion in total assets. The deal also expands Mercantile's recent focus on Northern Virginia and suburban Washington, D.C. Shares of James Monroe jumped $4.36, or 23% Monday to close at $22.90. Mercantile's shares fell 24 cents to $38.76.