E-mails allegedly written by Facebook co-founder Mark Zuckerberg are cited in a new court filing by Paul Ceglia as proof of his claim that he’s entitled to 50 percent of the company under a 2003 contract.

The revised complaint, filed in federal court in Buffalo, N.Y., includes new allegations supporting Ceglia’s claim to own part of Palo Alto, Calif.-based Facebook, the world’s biggest social networking site, including that Zuckerberg sent numerous e-mails discussing the terms of the contract and the early development of “The Face Book” with Ceglia.

“They’re exactly what you would expect between two people trying to develop a website,” said Robert Brownlie, a lawyer for Ceglia, of the e-mails.

Ceglia alleges that Zuckerberg defrauded him, lying about the early success of “The Face Book” at Harvard University, where Zuckerberg was a student at the time. Ceglia claims he is entitled to half of Facebook, a closely held company worth as much as $55 billion, according to Sharespost.com, an online marketplace for investment in companies that aren’t publicly traded.

On the same day that Ceglia revised his complaint, a federal appeals court upheld the settlement of a years-long legal dispute dramatized in the Academy Award-winning 2010 film “The Social Network” that pitted Zuckerberg against former classmates from Harvard who accused him of stealing the idea for Facebook.