How to mount a specific file system on a disk image in OSX?
You should parse the output of hdiutil, and mount the filesystems you're interested in - because you can't do what you're trying to do with mount.

The first few lines of the man page show supported syntax:

 mount [-adfruvw] [-t lfs | external_type]
 mount [-dfruvw] special | node
 mount [-dfruvw] [-o options] [-t lfs | external_type] special node


Notice for -a, there are no options to specify a node path, which makes your command invalid syntax.

(Also, I'd suggest testing with a proper image file - one that is an actual CD image.  Your image is a hard-disk type, with an Apple Partition Map, and no non-HFS partitions.  In Disk Utility, choose New -> Blank Image and note all the selections carefully.  You want "CD/DVD"; you can then edit the partition map after you've created it; say, to change to two partitions.)