FORT PIERKE FOSSILS. 95 



estimated about 1,050 feet above the sea. Ou each side, within a mile, the 

 plateau of the Pembina Mountain, which the inver cuts thn)ugh, rises 400 to 

 450 feet higher. A l)hiff 150 feet high ascends steeply from the fish trap 

 on the southwest side, and at the time of my first visit, in August, 1885, was 

 newly exposed by slides, being shown to be fissile, dark-gray shale to the 

 height of 100 feet, capped by glacial drift. The shale of this lower part of 

 the Fort Pierre formation is more sandy, softer, and darker than that of its 

 upper part, seen on the North Branch of Park River, and it further diifers 

 noticeably in having few joints. It is horizontally laminated, and, wliere 

 it has been somewhat dried on the surface of the bluff, is easily separated 

 in layers from a quarter of an inch to 1 inch thick; but at a depth of only 

 2 oi" 3 feet within its mass, where it is moist, no lamination is discernible. 

 In this shale crystals of selenite 2 or 3 inches long are frequent, and the 

 same mineral occurs in its crevices and seams. No lignite is found here, 

 nor in any of the other outcrops of this formation along the whole extent 

 of the Pembina Mountain to the south and north. 



My second visit to this locality was made in August, 188.i, to search for 

 fossils, though none were found the year before. Only the upper 20 feet of 

 the shale was visible in place at this later time, as the lower part, previously 

 exposed almost to the level of the river, was concealed by the talus of fallen 

 shale and drift. A portion of the shale beds 2 to 3 feet thick, about 10 feet 

 below their top in this section and 90 feet above the river, not distinctly 

 contrasted in color or texture with the beds above and below, was found 

 to have an odor resembling that of petroleum, and to contain sparingly, 

 on the planes of bedding, impressions of ScapJiites nicoUefii Morton, of 

 which about a dozen specimens were collected, and occasional casts and 

 fragments of Iiioceramus and Osfrea species, one being probably Inoceranms 

 sagensis Owen. From a mass of shale in the talus numerous cycloid fish 

 scales, and a vertebral bone, 1| inches in diameter, belonging to some 

 selachian fish, were obtained. If the formation is level in its stratification 

 from south to north, as seems to be the case, this outcrop presents a portion 

 of it approximately 200 to 300 feet lower than the bottom of its exposures 

 on the North Branch of Park River. 



