Authorities today named the three unidentified victims of an apparent serial killer who were dumped on a Long Island beach.

— Melissa Barthelemy, 24, from the Bronx, was last seen on July 12, 2009 in the Bronx.

–Amber Lynn Costello, 27, from North Babylon, was last seen on Sept. 2, 2010 in North Babylon.

— Maureen Brainard-Barnes, 25, from Norwich, Conn., was last seen on July 9, 2007.

Megan Waterman, the fourth victim, was identified last week.

Suffolk County cops said all four were killed in a similar manner but they declined to disclose how. They did say they believe murders were committed by a serial killer.

All four had advertised prostitution services on the Internet, cops said.

They each were dumped in the Gilgo Beach area of Long Island in burlap sacks. The bodies were discovered last month.

Cops said they don’t believe that there are more victims on the beach but plan to search again in the spring when the weather is better.