NEW YORK — An organized crime boss was sentenced to 18 months in prison for his role in an illicit relationship between his group and a union that represents many of the city’s school bus drivers and matrons.

Matthew Ianniello, aka “Matty the Horse,” was found guilty of collecting unlawful labor payments from officials of Local 1181 of the Amalgamated Transit Union and of obstructing a grand jury investigation of the union and the Genovese Organized Crime Family of La Cosa Nostra.

Authorities said that various officials at Local 1181 regularly received illegal payments from city-contracted school bus companies in exchange for favorable treatment from the union. Ianniello was found to have used his status as acting boss of the crime family to assist the union officials in obtaining the payments.

In addition to 18 months of imprisonment, Ianniello was sentenced to three years of supervised release, a fine of $25,000 and a mandatory $100 special assessment. He was also ordered to forfeit $75,000, which authorities said represents the proceeds of his criminal activity.