The Commission has determined that a county constituency be created from:The Merthyr Tydfil and Aberdare UK Parliamentary constituency,and:The Pontypridd UK Parliamentary constituency.
Mae’r Comisiwn wedi penderfynu creu etholaeth sirol o’r canlynol:Etholaeth Seneddol y Deyrnas Unedig Merthyr Tudful ac Aberdâr,ac:Etholaeth Seneddol y Deyrnas Unedig Pontypridd.