Chairman of Philadelphia Stock Exchange Quits

PHILADELPHIA — The chairman of the Philadelphia Stock Exchange, Vincent Casella, resigned Wednesday after an internal probe of his ties to a firm hired to implement an electronic trading system.

“Mr. Casella offered to submit his resignation to the PHLX Board of Governors,” the exchange said in a statement after a board meeting about the investigation.

At the meeting, the board heard the report by a special committee formed to investigate whether Casella improperly benefited from his ownership of shares in Ashton Technology Group Inc., which was hired by the exchange to build the trading system.

“The special committee unanimously recommended that the board accept Mr. Casella’s offer [to resign] and the board unanimously voted to do so,” the exchange said.

The exchange is an international leader in foreign currency options trading, as well as a market for sector-index options and other financial instruments.

Casella was listed in documents submitted to federal regulators as owner of 152,000 shares in Ashton, through a firm in which he was a principal, shortly before the firm went public in May.

An Ashton subsidiary, Universal Trading Technologies Corp., received the contract to build the system on the exchange’s equity floor. Ashton listed the contract in federal documents as a major source of its business.

Casella had been reported as defending his position in a letter to the board and exchange members by saying his actions were “totally motivated” by the “best interests of the exchange,” and by calling allegations of improper ties politically motivated.