Node Shader and Principled BSDF not in the node list. I was excited about the Principled BSDF but it did not appear on the new download 2.78c. Along with this I was following a tutorial and discovered that when I hit shift A for adding nodes that the shader was not in the list.
Besides being in the wrong version of blender ( for the Principled BSDF you need version 2.79, currently only available as a test build), you are looking at the compositing nodes, not the ones for materials.