Arcana Coelestia # 1148
1148. 'After the Flood' means from the time when this new Church emerged. Similarly this is clear from what has been stated in previous chapters. Actually the end of the Most Ancient Church and also the start of the Ancient Church is described by the Flood. It should be noted that the Church before the Flood is called the Most Ancient Church, but the Church after the Flood the Ancient Church.
Arcana Coelestia # 533
533. Since nothing further is mentioned about Lamech apart from the fact that be beget sons and daughters, who are the conceptions and births of such a Church, there is no need to pause any longer over him. What these births, or sons and daughters, were, becomes clear from the Church, for the character of a Church determines that of its offspring. Both those Churches called Methuselah and Lamech breathed their last just before the flood.