NATCHEZ — On the same day shareholders were to vote on the merger of Callon Petroleum and Carrizo Oil & Gas, the two companies announced new terms as a last-minute effort to save the deal.

Callon and Carrizo officials announced the amended merger agreement in a news release Thursday morning.

Officials rescheduled the vote on the merger by the shareholders of both companies for Dec. 20.

The announcement comes one week after one of Callon’s largest shareholders, Paulson & Co, Inc., announced it was voting against Callons’ acquisition of Carrizo.

On Nov. 6, the New York investment firm issued a news release stating that it had voted against the original deal. Paulson & Co. is Callon’s third-largest shareholder, owning 9.5% of the company’s shares. In the news release, Paulson & Co. stated that proxy advisory firms Glass Lewis & Co. and Institutional Shareholder Services had recommended that Callon shareholders reject the original deal.

In the new deal, Carrizo shareholders are to receive 1.75 Callon shares of Callon stock for each share of Carrizo stock. That number is down from the 2.05 Callon shares that were proposed in the original deal.

Under the new terms, Carrizo shareholders will own 42% of the combined company, down from the 46% initially proposed.

Callon President and CEO Joe Gatto said the amended agreement comes after discussion with shareholders.

“Since announcing the (original) transaction, we have had extensive and valued dialogue with our shareholders, who have expressed support for the industrial logic and strategic merits of this transaction,” Gatto said. “In recognition of evolving investor expectations for a successful combination in the current environment, we have agreed to revised terms with Carrizo that enable value-creation opportunities for both shareholder bases.”

Since the company merger was announced in July, Callon stock has declined from $6.71 on July 10 to $4.46 on Wednesday — a more than 30% decline.

Paulson and Co. said in a Sept. 9 letter to the Callon Petroleum Board of Directors said the stock’s decline “demonstrates shareholder dissatisfaction with the deal and its terms.”

In its Nov. 6 news release, Paulson & Co. recommended that Callon might be better off as a standalone company.

“A standalone Callon would be less risky and, combined with a reduction in its own operating costs, a shorter path to shareholder value than an overpriced acquisition,” the news release said.

The news release also said Callon should consider following the will of its shareholders and focus on, among other things, “engaging new, independent advisors to pursue a sale of Callon.”

Even with a new amended merger agreement, Callon and Carrizo officials say they expect to close the deal before the end of the year.

“Our strategy remains unaltered: we are creating a leading oil and gas company with a larger cash flow base to employ more efficient scaled development of our pro-forma Permian Basin position of over 100,000 net acres,” Gatto said in Thursday’s news release.

In a letter to employees Thursday, Callon and Carrizo officials said the decision to amend the merger agreement postpones employee decisions for the combined company.

“As a result of the revised timeline to close the transaction, we have made the decision to communicate employee placement decisions for the combined company early in the new year, after the holiday season, regardless of when the merger closes,” the letter said.