A week after announcing plans to scale back its trading-floor operations, the New York Stock Exchange’s parent company said Wednesday that it will lay off more than 500 staffers.

NYSE Group Inc. said it is cutting its work force by about 400 employees and 120 full-time consultants, as part of an ongoing effort to reduce costs. The company didn’t identify which jobs would be cut, but a person familiar with the matter said some of the layoffs may come from the NYSE’s trading floor. The job cuts won’t affect the Big Board’s self-regulatory arm, the NYSE said.

The layoffs, which will take place by next March, underscore the 214-year-old NYSE’s recent shift toward electronic trading. Last week, the company said it was shuttering the newest of its five trading rooms. Two days later, the NYSE said it had seen a “dramatic increase” in electronic trading in the first month under its new “hybrid market” system, which lets investors choose whether to trade in dozens of stocks via computer or the exchange floor.

“It’s a rough day,” an NYSE employee said yesterday when asked about the job cuts. “People are sad.”

The NYSE has eliminated about 35% of its nonregulatory work force, since March 2005, when the Big Board and Archipelago Holdings and Securities Industry Automation Corp., both of which the NYSE has acquired, had 3,484 employees on an adjusted basis.

More job cuts are possible but not yet planned, according to the person familiar with the matter. The work-force reduction is part of NYSE Group’s plan to wring out about $200 million in cost savings from the Archipelago merger, which closed in March.

Individuals whose positions are being eliminated will receive separation packages, and those eligible will receive outplacement services and retirement benefits, the company said.