I think the OP is referring to the second collect at the Christmas Day Mass at dawn, which in the Tridentine missal commemorated St. Anastasia, who was martyred on Christmas Day during the Diocletian persecution. Like all second (or third, fourth, etc.) collects, it immediately followed the collect of the Mass of the day.
No, it is not in the new missal, because the new missal limits the number of collects, prayers over the gifts (formerly the secret) and post communion prayers to one. There are no longer commemorations made of any other saint or event, other than the single collect for the Mass which is being said.