Perhaps I should have looked at this link before Ray's.
The funny thing is that across the pond we have always known this as a Griffiths Gnat even without the Peacock Herl. Great thing about fly tying is that you are always learning something new everyday!
From what I recollect, Griffiths Gnat originated on the same river, the Au Sable, this link takes you to a short description in Catches. Griffiths Gnat
Lady's Fish Finder, one to remember.