100 Cincinnati Societi/ of Natural History. 



line to New Mexico^ but on the Lower Missouri, where it was first ob- 

 served by geologists, it never reaches a thickness of more than 150 or 

 200 feet. In New Mexico it occurs as the most conspicuous of the 

 Cretaceous divisions, and along the line of the Kansas Pacific Railway,, 

 in Kansas, it has yielded large quantities of the most remarkable rep- 

 tilian remains. 



The Niobrara Group is found, in some form, whereverthe CretaceouS' 

 beds occur, from the north line to New Mexico, and probably much 

 farther. As it is developed on the Lower Missouri, and southward 

 through Nebraska, Kansas, into Texas and the Indian Territory, it 

 contains thick, massive beds of chalky limestone. On the Kansas^ 

 Pacific Railwa}^, at Forts Haj^s and Wallace, this limestone i& sawed 

 into blocks of any desirable size, with a common saw, and used for 

 building purposes; but along the flanks of the mountains, or in the 

 far west, it never reveals its chalky character. It is found in thin, 

 slaty, calcareous la3^ers, but universall}' characterized bj- the presence 

 of the oyster Ostrea congesta^ and also some form, of Inoceramus, or 

 a few fish remains, but the little oyster is ubiquitous. In these 

 three divisions there seems to be no well-marked line of separation^ 

 and the more we study them the more intimately do they seem to 

 be blended together. 



The Fort Pierre Group begins to overlap the Niobrara Group 

 below the mouth of the Niobrara, and above that point, although the 

 river cuts deep down into the chalk limestone, and long lines of cone- 

 like bluff's extend up nearlj^ to the Great Bend, yet the distant hills 

 on either side of the river show plainly the dark shaly claj^s of this 

 group. -This group covers a vast area of country, perhaps 5,000 

 square miles or more, and wherever it prevails, it gives to the sur- 

 face the aspect of desolation. The entire thickness of the group is 

 filled with the alkaline material, which is so well known in the west, 

 and -wherever the water accumulates in little depressions and evap- 

 orates, the surface is covered with a deposit of the salt varying from 

 an inch to several inches in thickness. The water that flows throuo-h 

 these clays is usually impregiTated with these salts and thus rendered 

 unfit for use. Although these clays seem to be so sterile, and in the 

 dry season are typical of extreme aridity, yet the3^ are b}^ no means 

 destitute of vegetation. The various species oi chenopodiaceous shrubs 

 and herbs, that are peculiar to the west, find their natural habitat in 

 these clays, and grow most luxuriantly. The Sarcobatus reaches its 

 highest growth in this region. The somber appearance given to the 

 country by the black clays is unfavorable to it. At the Great Bend 



