The best I could do for a genealogy here was a site that said Mary Lynn McKenzie is a cross between Cattleya Bob Betts and Cattleya Swan. This isn't especially exciting information to know, and this is the internet so it's always possible that it isn't even true information, but I'm including it in the post anyway because really, the only commentary about this flower I can come up with is that it's awfully white. Which you already know, having seen the picture already.
I also kind of approve of the weird white-daffodil impression it's doing. It amuses me when plants imitate one another.