The Wilton and Deerfield barns appear to match the description provided thus far of typical CG frames but the Shirley barn is quite different in that it has interrupted wall plates that join into the ends of the tie beams rather than connecting girts which join lower down into the posts. More importantly this barn also has an "additional" set of horizontal dragon ties which connect the tie beams to the wall plates and this is a really archaic practice which died out in England in the 1300 / 1400's and yet here it is reappearing centuries later in Massachusetts.
It is debateable whether the Shirely barn is a major CG variant or actually belongs to a completely different classification and hence I think that it is certainly worth consulting Jack Sobon's Historic American Timber Joinery Series - Part II - Tie at Plate (downloadable from the TFG website) where Jack features this very joinery configuration in figure 31 & 32 on a 1850's barn previously located at Shrewsbury, Mass.
Don,
The Shirley barn may be a good one to feature in your research articles.
