Gnus and Preview.app on a Mac

[Alex Schroeder]

In an old message I saw Lars say, that using ~/.mailcap should do 
the trick. So I tried this:

application/pdf; open %s

When I look at my *Messages* buffer, I see the following:

Displaying open 
/var/folders/tv/tvbc\+bneEXWIKBV8nDtCXE\+\+\+TI/-Tmp-/emm.1878mQ/ZTS_Okt13.pdf...done

Then, nothing happens. When I check the path, I see no emm* 
directory.

alex@Pyrobombus:~$ ls 
/var/folders/tv/tvbc+bneEXWIKBV8nDtCXE+++TI/-Tmp-/
PreviewTemp-6d5jS3/ emacs501/           
docview501/         xcrun_db            

Something is not working correctly. Any ideas?

Cheers
Alex