Dec 11 (Reuters) - Gold miner Perseus Mining ( PMNXF )

said on Thursday its binding offer to acquire Predictive

Discovery ( PDIYF ) has lapsed after rival bidder Robex Resources ( RSRBF )

improved its bid proposal under an existing agreement.

The companies, all with gold assets in West Africa, are

vying to expand amid this year's record prices for the yellow

metal.

Perseus' now-lapsed offer valued Predictive at A$2.1 billion

($1.4 billion) and carried a 24.5% premium to Predictive's close

on December 2, the day before the offer was announced.

Robex on Thursday amended its existing October 5 agreement

to match Perseus' bid.

Under its improved proposal, Robex shareholders would now

receive 7.862 fully paid ordinary shares in Predictive, for each

Robex share, valuing Predictive at A$2.17 billion.

In its previous offer, Robex shareholders got more

Predictive shares than in the current offer, with the rising

valuation largely a function of gold prices on the share values

of the companies.

Upon completion of a deal, existing Predictive shareholders

would hold about 53.5% of the combined entity, with former Robex

shareholders owning 46.5% on a fully diluted basis.

The deal comes as global gold prices have repeatedly hit

record highs this year amid expectations of lower U.S. interest

rates.

Shares of Predictive Discovery ( PDIYF ) fell 9.9% on Thursday, set

for their worst day since May 28. Perseus Mining ( PMNXF ) advanced 3%.

Robex shares were not trading at the time of the

announcement. They finished on Wednesday at C$4.40, down 0.1%.

($1 = 1.4990 Australian dollars)