We have a Triton (2000) here (It's ancient and I haven't updated the firmware on it in forever) and so I pulled it out to remind myself why it's not listed on the compatibility list. The device is Windows CE based (at least the version that I have is) and as such, they use special windows protocols to communicate. I was never able to get it communicating over USB. If you have an SD card, you can use that and LoadMyTracks.
Sadly, Magellan has a basic Mac App to talk to some of their devices, and the Triton series is not included.