[Iaurhirwen]

That ancient Arturian land sounds a lot like Numenor. The entire idea that this island, Lyonnesse, was once the home of the fragments of a forgottten people is quite similar to the idea of the house of Elros settling here and the rest of the men of Middle Earth forgetting about their existance.

I'm not quite sure if Lyonnesse and Atlantis are the same location though. From what I can remember from my studies, the ancient city of Antlantis was supposed to have sunk into the sea during the ancient times, hundreds of years before the time of Arthur. The statement must be made, however, that the similarites between Antlantis, Lyonnesse, and Numenor are very striking, and that there is possibly a connection between the three.