FORMATION 3 OF THE NEBRASKA SECTION. 323 



separate position in the series. It is composed of a dark 

 leaden grey, laminated, plastic clay, containing few fossils, 

 but great quantities of the sulphate of lime in crystals, 

 assuming a variety of beautiful forms. Its greatest thick- 

 ness is seen five miles below the mouth of James Eiver. 

 At Dorion's Hills it is seen at low water mark. Entire 

 thickness estimated at ninety feet. Fossils, Ammonites, 

 Inoceramus, Cytheria, Serpida, Ostrea, and abundant fish 

 remains.] 



This formation has been recognized on the Assinniboine. 



On the North Branch of the Saskatchewan, a few miles 

 above the Grand Forks, huge masses of a dark coloured, 

 almost black shale, with sharp, well-preserved edges jut 

 out of the banks and are exposed whenever portions of 

 the face of the clay cliffs fall into the river. Their ap- 

 pearance is such as to justify the expectation that rock in 

 position from which they originated is close at hand. 

 Some specimens which I procured and sent to Mr. Meek, 

 contain, according to that gentleman, fish scales, sharks' 

 teeth and Inoceramus, which renders it almost certain 

 that the masses were detached from rocks belonging to 

 Formation 2 or 3, of the vertical section. I have there- 

 fore assigned in the foregoing table, the locality Coal 

 Falls, North Branch of the Saskatchewan, with a note of 

 interrogation, as the probable outcrop of one or both of 

 these divisions of the vertical section. 



FORMATION NO. 3 OF VERTICAL SECTION. 



[The geographical distribution of this formation and 

 its influence on the scenery render it one of the most in- 

 teresting on the Missouri. It is first seen in thin outliers 

 near the mouth of Big Sioux Eiver, and becomes quite 

 conspicuous on the summits of the bluffs, ten miles above 

 the Iowa Creek. At Dorion's Hills, it reaches to the 



