In the detailed geologic mapping of the Wayan and Montpelier quadrangles, in south-eastern Idaho and adjacent territory, it has been found necessary to apply new names to strata hitherto referred to the Beckwith and Bear River formations or to portions of the Laramie as mapped by the Hayden Survey. The two quadrangles are contiguous, and the Montpelier quadrangle lies south of the Wayan. They occupy the corner of the State and include a very narrow strip in northeastern Utah and a somewhat broader strip in western Wyoming.