FOSSILS FOUND IN FOEMATION 4. 



327 



blue argillaceous shale, holding numerous concretions 

 containing a large percentage of iron. Some very obscure 

 fossils were found in it, with fragments of Inoceramus 

 Canadensis* The shale weathers ash- white ; and the 

 exposure on the Little Souris is seventy feet thick in 

 horizontal layers. 



Where the river has excavated a passage through the 

 Blue Hills of the Souris, the rock frequently occurs in 

 cliffs, the dip being 3° south. Fragments and perfect 

 forms, but very fragile, of Inoceramus Canadensis, are 

 very common. The ferruginous concretions are disposed 

 in regular layers, and constitute a marked feature of the 

 rocks of this valley. 



A few miles west of the Blue Hills the dip of a very 

 remarkable exposure of shale, with bands of ferruginous 

 concretions, facing the south, was leveled with the utmost 

 care, and found to be perfectly horizontal. At the base 

 of the exposure, and on a level with the water's edge, a 

 layer occurs full of gigantic Inoceramus, probably the 

 same species as those before-mentioned. One specimen 

 measured eight inches and a half in diameter, it was very 

 fragile ; but the peculiar prismatic structure of the shell 

 was remarkably well preserved. On attempting to raise 

 it, it separated into thousands of minute prisms. 



A search for fossils here was more successful, and re- 

 sulted in the discovery of several new species, which 

 were examined, named, and described by Mr. Meek of 

 Washington. 



On the Two Creeks, an affluent of the Assinniboine, the 

 same formation exists. Among the fossils collected there 

 were Natica obliquata, Avellana concinna, Ammonites 

 (sp. undt.), &c. &c. 



* See figure on p. 336. 

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