Section 49. No fee shall be allowed to a trial justice for issuing more than one mittimus, nor to an officer for the service of more than one mittimus, in cases in which two or more persons are jointly convicted and sentenced to the same place of imprisonment; and, if the superior court is of opinion that a trial justice has improvidently issued two or more warrants against the same defendants for similar offences, no fees shall be allowed to the justice upon any of said warrants.