A ranking of the biggest philanthropists in America, known as the Slate 60, might be more aptly named the Slate 61 this year with the late addition of one of the country’s leading philanthropists, Mayor Bloomberg.

Mr. Bloomberg’s name was missing from the original list of philanthropists published by Slate yesterday, but the record was corrected by evening after aides to the mayor, who gave away $205 million in 2007, contacted the online magazine to point out the omission.

A deputy editor of Slate, David Plotz, said no one would be removed from the list to make room for Mr. Bloomberg.

“I’m embarrassed. We screwed up,” Mr. Plotz said. “We never followed up with Bloomberg, which we should have done, because he had been a big donor for years.”

Mr. Bloomberg, a multibillionaire, often gives anonymous donations but has cooperated with the Chronicle of Philanthropy in the past, confirming the amount he has donated in a given year.

In 2007, Mr. Bloomberg donated $205 million to 1,100 nonprofit organizations in the arts, education, health care, and social services but refused to name the beneficiaries, the Chronicle reported. Slate, which is owned by the Washington Post Company, historically has partnered with the Chronicle to compile its annual list, but this year teamed up with the Center on Philanthropy at Indiana University, which Mr. Plotz said tracks philanthropists based on individual donations that are announced publicly. Mr. Bloomberg has appeared on the list for the past three years and delivered a keynote address at a dinner celebrating the Slate 60 list in 2006.

“Slate should be applauded for giving recognition to a group that truly deserves it, but doesn’t always ask for it,” he said during his speech, according to his prepared remarks.

A spokesman for Mr. Bloomberg, Stuart Loeser, wrote in an e-mail message that the city pointed out the omission but declined to comment further on the error.

Even with the addition of Mr. Bloomberg, Slate’s list still differs from the Chronicle’s ranking. The real estate tycoon Leona Helmsley, who died in August, has the top spot on Slate’s list, for donating $4 billion to the Leona M. and Harry B. Helmsley Charitable Trust.

The co-chairman of the Hilton Hotels Corp., William Hilton, was first on the Chronicle’s list and second on Slate’s list for giving away $1.2 billion last year.

Mr. Bloomberg is eighth on Slate’s list and seventh on the Chronicle’s list.