Ticker Talk:

Archipelago agreed Thursday to the final terms of a plan to buy the stock trading unit of the Pacific Exchange and form an automated alternative to the New York Stock Exchange and Nasdaq. Terms of the transaction were not disclosed. Archipelago is a privately held company whose owners include Goldman Sachs, Merrill Lynch and J.P. Morgan. The merger plan will involve the eventual closing of the Pacific’s stock trading floors. In their place Chicago-based Archipelago will open the electronic Archipelago Exchange, with trading in stocks listed on the NYSE, Nasdaq and the American Stock Exchange.