Hey,
I don't have any pictures of a feather duster but they are real easy to identify. When real small you wont see a tube, just a circle of feather looking fronds. When spooked they very quickly retract into the tube. When they get a little bigger, as some of mine have, you will begin to see a narrow tube sticking out of the rock with the dusters, or "head", at the end. HTH.
Dan'l