On my system (Mepis), if you insert a CD it automounts to /media/hdc--even though there is no corresponding entry in /etc/fstab.
If I then umount hdc, I can manually mount using:
mount -t iso9660 /dev/hdc /media/hdc (or any mount point)
But, I can NOT mount /dev/cdrom
If I umount and then delete all the mount points in /media, and then re-insert the CD, it auto-mounts and re-creates the /media/hdc mount point.
Please don't ask me to explain what is going on......