subtype isn't going to be the index in the mount journal. That's the actual subtype of the mount. If it's a water mount, flying mount, ground mount, etc, etc.
See here:
http://www.wowinterface.com/forums/s...504#post294988
/edit: though I notice 268 isn't included in Gello's list of type id's he's discovered. You might want to double-check yourself, and then post in that thread if that is the case.