The Order came into effect on 14 December 2011 so from this point onwards there are some differences between the Parliamentary constituencies and the Senedd Cymru Constituencies.
Daeth y Gorchymyn i rym ar 14 Rhagfyr 2011 felly o'r pwynt hwn ymlaen mae rhai gwahaniaethau rhwng etholaethau Seneddol y Deyrnas Unedig ac etholaethau Senedd Cymru.