Strange Tree, Strange Growth??

Climbing out on the hills at Acharacle again this morning and came across this tree that had fallen but continued to grow......as we approached we thought there was something like an old wasps nest attached just under the top of the branch.

Can anyone help identify this? It does not appear to be wood but is quite solid and lined all the way down.

It was funny enough seeing the shape of the tree but I would love to know what is attached to it.