* Misys shares rise 8.4 pct, Temenos down 0.6 pct

LONDON Feb 20 (Reuters) - Vista Equity Partners said it had made an approach to buy Misys in a cash deal that would scupper an agreed merger between the British banking software group and Swiss peer Temenos.

The Financial Times had reported that the private equity firm was lining up a 360 pence per share bid, valuing Misys at about 1.2 billion pounds ($1.9 billion).

Vista, which has offices in Chicago and San Francisco, invests in software and technology businesses. It bought Thomson Reuters trade and risk management business last year.

It said any offer for Misys would be subject to a recommendation from Misys' board of directors, it said.

Shares in Misys, which have fallen by as much as 14 percent since it announced the details of the Temenos deal last week, rose 8.4 percent to 335 pence by 1511 GMT. Temenos was down 0.6 percent.

Under the terms of the all-share tie-up with Temenos, the British group would take 53.9 percent of the equity, but Temenos' chief executive and chairman would lead the management team.

Misys was in talks with Fidelity National Information Services last summer, before the U.S. firm walked away.

Analyst Milan Radia at Jefferies said there was an opportunity for somebody else to gatecrash the Misys-Temenos deal because there was no upfront premium.

"360 pence is an opening gambit, and if four pounds is where we understand FIS left off in a slightly better market environment last August, then 380 pence to four pounds is probably a knock-out," he said.

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