Mac OS X Lion Developer Preview 2
Is a new version of mac, a beta one but more interesting with some changes.
The beta software, labeled Mac OS X Lion Developer Preview 2 and carrying build number 11A419, is available to registered developers through the Mac App Store after requesting a redemption code.
It was accompanied by Mac OS X Lion Server Developer Preview 2, also carrying the same build number, as well as Xcode 4.1 Developer Preview 2 -- a pre-release version of the Mac OS X development environment provided by Apple.