How to delete the overlapped vertices in a 3D model?

As you can see the image below, it is a human head model unwrapped in the UV/Image Editor. The selected vertices should be the overlapped vertices but I cannot delete them just by pressing Delete key. I can just delete it in the 3D View. However, it is difficult to select them in the 3D View. So, I want to ask that how to easily delete those overlapped vertices?

Unwrapped 3D Human Head in UV/Image Editor

Not certain if this is what you're looking for, but if you go into edit mode with tab, then select every vertice (by pressing a) and in the tool panel (press t to toggle), select remove doubles. That will remove vertices that closely overlap.