Continuing my "myrmecodia tuberosa" saga, I just bought a new one from Blackjungle, as the other one died, and this one is very healthy. I just need care info for it.

Have you googled for cultural requirements? As I recall there's a fair amount online.

As far as the Rhipsalis goes, I've never tried one. I know it's a succulent and read somewhere that they do like regular watering but don't like to stay too wet. That said, you might be keeping it too damp. IME with other tropical succulents, I found that until they actually root, it is best to keep them a bit more on the dry side. Whether this is true for Rhipsalis I honestly don't know. The blackening area sounds like rot. If any of the cuttings are still looking good (assuming you have more than one), it might be best to try planting it in a more free draining medium. Perhaps it will root there. If it does and the worst happens to the rest of the mounted ones, you would then at least have a growing plant to then try again with. Wish I could be of more help. Attached is a link to site that may help you with ID

Here is a link that might be useful: Rhip ID guide

Yes I have googled it.
I looked at the website you attached, and the Rhipsalis looks alot like R. Dissimilis (spelling?) It doesnt feel like rot, I took it off it's mount just to check if it was rot. I am assuming that airial (once again, spelling?) roots count as roots, as it has made airial roots off of some of the Stem (maybe leaves, it is hard to tell with Rhips.) axils. Blackjungle sent me extra cuttings by mistake, so it IS good to make mistakes sometimes, Lol. So I put the healthiest,biggest cutting into the terrarium. I put the other cutting in a pot with sphagnum.

Thanks,
Chris

If those are aerial roots (correct spelling *wink*), you might -- if you haven't already -- remove the plant, turn it around, and remount it with the roots in contact with the mount. I've done things like that with some of my mini orchids.