Petsmart Earnings Rise, But Shares Slump  NEW YORK (Reuters) - Petsmart Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=PETM.O target=/stocks/quickinfo/fullquote"&gt;PETM.O&lt;/A&gt;, the top U.S.  pet supplies chain, on Thursday said quarterly earnings rose on  improved pet services sales, but its stock sank as much as 12  percent as results lagged analysts' expectations.