In corporate news, Knight Capital Group ( KCG) shares extended the prior session's gains as it popped by 5.3% following a report from The Wall Street Journal that the firm may sell its market-making business, the company's most profitable unit. The Journal reported that Knight had been approached by at least two competitors about buying the business.

Corning ( GLW) shares popped 6.9%. The glass manufacturer announced expectations of stronger-than-forecast fourth-quarter LCD glass volume and full-year sales of Corning Gorilla Glass approaching $1 billion, amid stronger-than-expected retail demand for LCD televisions and other consumer electronics devices in North America and China.

Ralcorp Holdings ( RAH) shares surged 26.4% after the private-brand food products company announced that ConAgra Foods ( CAG) will acquire all outstanding shares of Ralcorp for $90 a share in cash.

Ralcorp on Tuesday also revealed better-than-expected fourth-quarter earnings of 92 cents a share; analysts, on average, were expecting earnings of 87 cents a share. Revenue came in at $1.07 billion, compared with expectations of $1.1 billion. ConAgra shares tacked on 4.7%.

Shares of Green Mountain Coffee Roasters ( GMCR) were soaring more than 20% in extended trades after the company trounced Wall Street's expectations for its fourth-quarter results, reporting a non-GAAP profit of 64 cents a share with net sales rising 33% year-over-year to $946.7 million, well ahead of the consensus view for earnings of 48 cents a share on revenue of $902.7 milion.

The board of Las Vegas Sands ( LVS) declared a special dividend of $2.75 a share after Monday's closing bell. Shares jumped 5.3%.

Dollar General ( DG), the discount retailer, will join the S&P 500, replacing Cooper Industries ( CBE), which is being acquired by Eaton ( ETN).

Dollar General shares finished up 0.41%.

Equity Residential ( EQR) and AvalonBay Communities ( AVB) agreed Monday to jointly purchase the assets of Archstone Enterprise LP, mainly a portfolio of apartment properties, from Lehman Brothers.

Equity Residential shares gained 1.5% and AvalonBay shares rose 2.6%.

Yelp ( YELP) shares bumped up 6.6% after being upgraded to buy from hold at Cantor.

Acadia Pharmaceuticals ( ACAD) shares soared 136.1% after the company announced that its experimental antipsychotic treatment exhibited solid progress in a phase 3 trial in treating patients afflicted with Parkinson's disease psychosis.

-- Written by Andrea Tse and Joe Deaux in New York.

>To contact the writer of this article, click here: Andrea Tse.

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