It is the purpose of this paper to give the results of petrgraphic studies of hte Hygiene Sandstone members of the Pierre shale by applying well known standard methods of sedimentary investigation to this untried type of marine sand in an effort to ascertain whether or not these methods can be satisfactorily used for lateral correlation purposes. In addition, it was hoped that such an investigation might possibly reveal more information concerning conditions of Pierre sedimentation in the region of Boulder, Colorado.