Wolf refused the stipend, she said, because she was the author of the proposal that enabled the school committee to pay its members. Vellucci said he had the money donated to purchase violins for Cambridge public school students.

Wolf said yesterday that she had understood the mayor's salary, after 1988, to include the compensation.

Vellucci agreed. "Evidently [Reeves] must have made a mistake," Vellucci said last night. "He probably didn't know that."

Ball said the oversight began in October 1992 when Claire E. Rodley, the school committee secretary, informed Reeves that he not been receiving his stipend since he took office in January.

"A check was then issued to me, retroactively paying me the salary I had not received, and a check was issued to me each week thereafter until I discovered the error," Reeves said Monday.

Rodley defended her mistake yesterday. "Other mayors had been paid," she said. "To the best of my knowledge, he was entitled to be paid the same as the mayors before him."

Ball also defended Rodley's actions.

"The city council may have voted on the increase, but the school committee never received a paper saying, 'Stop paying the stipend," Ball said.

Reeves said he had noticed the difference on his W-2 tax forms between his salary and that of the other eight councillors. But he said he assumed the difference was equivalent to the value of his Ford automobile. The car is provided by the city for the mayor's use, but is subject to taxation.

Reeves said he asked City Manager Robert W. Healy to investigate the overcompensation last week.

"I must unequivocally state that at no time have I been aware that I have been paid more than was due to me," Reeves said Monday.

City officials yesterday criticized a bureaucracy that allowed two salaries to exist for one job.

Alfred B. Fantini, a school committee member, said the city auditor should have detected the mistake years ago.

"It's probably embarrassing to say, but it fell between the cracks," Fantini said yesterday. "There's a checks-and-balances that needs to take place in the city auditor's office that doesn't take place."

James Conry, the school department's finance manager, did not return repeated phone calls yesterday.