So here's the mystery: this type of dress (worn by Queen Victoria here) is supposedly (according to ) known in America as a "Boston dress."
However, I can't find any other confirmation (other than that book of paper dolls linked above) of this term. Anyone want to take a shot at seeing if it's in any of the full-text newspaper databases? Or JSTOR? Or Making of America?
The person with the oldest printed citation/example will get a copy of the book (not a copy of the Winterhalter portrait, sadly).
Have fun looking!