IOWA ACADEMY OF SCIENCES. 21 



the fossils were imbedded at essentially the same horizon, then those that 

 now occupy the lowest level haye been longest exi^osed to atmospheric and 

 aqueous agencies. 



At Hot Springs, about twenty miles as one has to travel from the prin- 

 cipal group of cycads, the valley of Fall river has been cut down through 

 the entire thickness of the Dakota sandstone, through all the Jurassic, and 

 down into the purple limestone and gypsiferous red clays of the Red Beds. 

 Battle Mountain, east of the town of Hot Springs, has an elevation of about 

 a thousand feet above the valley. The upper part of the mountain is com- 

 posed of the Dakota sandstone, and away up at the summit is the quartzite 

 seen on the higher eminences around Minnekahta. Fall river, formerly 

 known as Minnekahta creek, Hows off toward the southeast to join the south 

 fork of the Cheyenne river. About four miles from Hot Springs, the stream 

 emerges from the sandstone hills in a series of cascades which constitute 

 the falls of Fall river. At the falls, as previously observed by Newton, the 

 sandstone is inclined at a high angle and passes beneath the dark colored 

 shales of the Fort Benton group. Crossing the nearly level plain that sep- 

 arates the last of the sandstone hills from a high escarpment that curves 

 around nearly parallel to the mai'giu of the uplift, we tind ourselves on cal- 

 careous beds of the Niobrara group. These are charged with Inoceramus 

 prohlemaiicus Schlotheim, with occasional colonies of Ostrea congesta, the 

 whole aspect of the formation resembling closely the Inoceramus bearing 

 beds near Sioux City, Iowa, and Pouca, Nebraska. The similarity of the 

 Sioux City deposits to Niobi-ara beds on French creek, a locality probably 

 thirty miles northeast of the point just noted, was remarked by Prof. N. H. 

 Winchell in 1874. 



Over on the Cheyenne river, about six; miles east of Fall River Falls, is an 

 exposure of Niobrara that reminds one of the massive chalk beds at St. 

 Helena, Nebraska. The resemblance is not complete, for at St. Helena the 

 beds are for the most part white, only occasionally portions are bluish in 

 color owing to the pi'esence of organic matter. On the Cheyenne the beds 

 are all bluish. They give out a strong fojtid odor when struck with the 

 hammer. There are indications of the presence of organic matter in 

 unusual amount. But the massive bedding of the soft, calcareous material, 

 the manner in which the layers break down, the huge blocks of talus, the 

 occasional small colonies of Ostrea congesta, the vertebrre and scales of 

 fishes, are each and all perfectly duplicated at the two points mentioned; 

 namely, on the Missouri at St. Helena, and on the south fork of the 

 Cheyenne southeast of Hot Springs. 



Around Edgemont, south of the hills, the country for some distance is 

 occupied by the Fort Benton shales. A steep escarpment which constitutes 

 the vertical face of the first terrace south of Cheyenne, reveals with their 

 usual characteristics, the Inoceramus beds of the Niobrara: but passing on 

 southwest over the hills toward the valley of Cottonwood creek, the Fort 

 Benton is again exposed. Erosion of the shales has formed a series of Bad 

 Lands on a diminutive scale. It has at the same time made proiuinent cer- 

 tain beds of impure limestone, from which we obtained numerous fossils. 

 Among the collections here were specimens of Prionocyclus wyomingensis 

 Meek, Scaphites warre?ii. Meek, Lunatia coticiniia M. and H., Lioceramus 

 pseuclo-mytiloicles Scheil. two or three other species of Inoceramus, a Pteria 

 or two, and many other less obtrusive forms that have not yet been identified. 



