Police officials on Wednesday announced the identities of a woman and her 2-year-old child, whose bodies were found near the desolate stretch of Long Island seafront that was the scene of the Gilgo Beach serial killings.

The woman had long been known as Jane Doe No. 3 — or “Peaches,” after a fruit tattoo — and was thought to be the mother of a toddler whose body was also found along the South Shore’s beachfront. She was Tanya Denise Jackson and her daughter was Tatiana Marie Dykes, Detective Sergeant Stephen E. Fitzpatrick of the Nassau County police department said at a news conference.

Rex Heuermann, a Massapequa Park, N.Y., architectural consultant, has pleaded not guilty to killing seven women, including six whose remains were found off Ocean Parkway. But until Wednesday, three of the 10 Gilgo victims found in the area, and in nearby Southampton, had not been identified. The authorities did not say whether they believe Mr. Heuermann killed Ms. Jackson and the child.

“I’m not saying it is him, I’m not saying it’s not him,” Sergeant Fitzpatrick said.

Although the Gilgo killings have primarily been investigated by Suffolk County officials, Wednesday’s announcement was made by the police in Nassau County, where Ms. Jackson’s remains were first discovered. Pieces of her body were found in 1997 at Hempstead Lake State Park in Nassau County, several miles from the New York City border. Her other remains were found in 2011 near Gilgo Beach.

The body of Tatiana, who was found in a thicket of branches, wrapped in a blanket and wearing gold jewelry, was discovered in April 2011 along with the nearby remains of Ms. Jackson. The child was about 2 years old at the time of her death, the police said. Her remains have been linked to Ms. Jackson by DNA analysis conducted as part of the broader Gilgo investigation.

Investigators have asked the public for help in identifying the remaining victim, an Asian man.

This is a developing story and will be updated.

Nate Schweber contributed reporting.