Prevent Finder from Automatically Mounting All Partitions on a Single Volume

[ac3320]

Is there a way to prevent Finder from automatically mounting all of the partitions on a single volume? For instance, I keep an external HD connected via USB and use it as my backup destination for Time Machine. On the same external I have another partition which is a bootable copy of the latest version of OS X.

I want the Time Machine partition to mount, in case I want to do some Finder browsing of older files. What I do not want is for the bootable 10.8 partition to mount as well.

Any ideas?

Here's what it looks like when I insert the USB cable:



And here is the partition I do not want to automatically mount upon inserting the USB cable.


There's gotta be a way to do that. Maybe by making it "Hidden?" That's how Disk Utility show the Recovery HD partition, which does not automatically mount on the Desktop. I was not able to ascertain how to do this with my external HD :/