Petro-Canada, Calgary, (NYSE: PCZ; Toronto: PCA) has made an unsolicited offer for Canada Southern Petroleum Ltd., Calgary, (Nasdaq: CSPLF; Toronto: CSW) for US$7.50 in cash per share, or approximately US$113 million total. Canada Southern Petroleum has producing assets in the Yukon Territory, north-eastern British Columbia, southern Alberta and land holdings in the Canadian Arctic. The offer price represents a premium of approximately 58% over the closing price of Canada Southern's shares and approximately 45% over the volume weighted average trading price for the 30 trading days ending May 10. The offer will be made through Petro-Canada's subsidiary Nosara Holdings Ltd. and funded from Petro-Canada's cash on hand. It is conditional on acquiring at least 66.66% of all outstanding Canada Southern shares.