Caption from U.S. Geological Survey Open-file Report 70-333, Plate 3 Figure E - Zone near center pf picture is shaly crystalline dolomite in upper member of Pilgrim Limestone. Scale is about 6 inches long. See Figure F. Published as Plate 3D in U.S. Geological Survey Open-file Report 70-333, Geology of the North End of the Ruby Range, Southwestern Montana. 1970.