R.H. Donnelley Corp. said Monday it is buying its larger rival Dex Media Inc. for $4.2 billion, creating the country’s third-largest yellow pages company.

The deal creates a major player in the increasingly consolidating yellow pages industry, which despite emerging threats from Google Inc. and Yahoo Inc. remains a highly profitable business that has attracted investors from big private equity firms.

The new company, which will keep the R.H. Donnelley name and be based in Cary, N.C., will operate more than 600 directories in 28 states. Donnelley currently publishes directories under the Sprint name, while Dex is the official directory publisher for Qwest Communications International Inc.