* S&P has ended higher 11 times in past 13 sessions
* Losses broad, but "momentum" stocks outperform
* Achillion Pharma jumps in heavy volume
* Dow, S&P 500 and Nasdaq all fall 0.1 pct (Updates to midday trading)
By Ryan Vlastelica
NEW YORK, June 10 (Reuters) - U.S. stocks fell modestly on Tuesday as investors found few reasons to keep buying with the Dow and S&P 500 coming off a string of record highs.
The day's losses were slight but broad, with eight of the ten primary S&P 500 sectors down on the day. The biggest declining group, industrials, was down a slight 0.4 percent, and some sectors were down 0.1 percent.
"Momentum" stocks, marked by hyper levels of growth and concerns over valuation, were among the day's biggest outperformers, with a number of Internet names also higher on the day. Facebook Inc rose 3.5 percent to $65.05 while Netflix Inc was up 2.7 percent to $434.51.
Tuesday's decline comes after a string of gains for Wall Street. The S&P 500 has ended at a record for the past four sessions, and ended higher 11 times in the past 13 sessions.
"Most valuation metrics suggest that equities are no longer cheap, though they're not exactly overpriced where they are now. People are looking for reasons to really buy, but we're optimistic that equities can continue to push higher," said David Carter, chief investment officer at Lenox Wealth Advisors in New York.
Investors continue to watch trading volume, which has been below average of late, potentially making the market more susceptible to big swings. The CBOE Volatility index rose 0.7 percent in its second straight daily move, though it remains at very low levels from a historical perspective.
The Dow Jones industrial average fell 13.02 points, or 0.08 percent, to 16,930.08, the S&P 500 lost 2.48 points, or 0.13 percent, to 1,948.79 and the Nasdaq Composite dropped 3.98 points, or 0.09 percent, to 4,332.26.
Achillion Pharmaceuticals Inc was the Nasdaq's most active name, surging 57 percent to $6.66 in brisk trading, building on a jump of almost 48 percent on Monday. The company early Tuesday commented on an ongoing Phase 1 clinical trial for a hepatitis C drug, and was upgraded to "market outperform" from "market perform" by JMP Securities.
Also boosting biotech names was Receptos Inc, which jumped 34 percent to $39.40 after its experimental multiple sclerosis drug met its main goal in a mid-stage trial.
RadioShack Corp slumped 9.7 percent to $1.39 after the U.S. electronics retailer reported a much wider-than-expected quarterly loss.
Chico's FAS Inc rose 9.7 percent to $16.86 in heavy trading after the Financial Times reported that the company was exploring a sale to private equity. (Editing by Nick Zieminski and Bernadette Baum)