Collisions layer is not appearing.

On my player object (or any object right now) I was trying to select the collisions layer. However that layer is no longer appearing as a standard layer. I opened an older project and the collisions layer was still there, but it is not in my new project. I did just update from Unity v4.2.0 to v4.3.4 and have been scanning the release notes to find something about the removal or change of the collisions layer. Does anyone know if it is gone or is no longer needed? I tried reinstalling Unity already, that didn't work.