Mo. Rev. Stat. § 547.100
If any person taking an appeal from the circuit court on a conviction for a misdemeanor shall fail to perfect the appeal within six months from the time the appeal is granted, the prosecuting attorney may file his motion before the court in which the conviction was had, asking that the appeal may be dismissed and the order granting the appeal be set aside; whereupon the court shall make an order that the appeal be dismissed and the order granting the appeal be set aside and for naught held, unless the defendant shall show to the satisfaction of the court good cause for not perfecting his appeal, in which case the court may overrule the motion, and from the date of making such order dismissing the appeal, the judgment shall be and remain in force the same as if no appeal had been granted.
§ 547.100, RSMo
Effective 1/2/1979