So apparently I don't have a systemwide default designated. OK
The vanilla setup of the 27-70-2003 binary of LyX on Aqua sets the viewers to "open" which would utilize whatever PDF viewer you have designated as the default for the Mac.
I did. It's gone when I restart.
If you prefer a viewer other than the system default, change it in your preferences and click "modify" before you do "save."
Lenore Horner
