In the Milk River Country 131 



We could have secured tons of these shells, that 

 to all appearances might have died yesterday. 

 Many had the original shell with its pearly lus- 

 trous layer attached to the inner cast of mud 

 that filled the shells. Usually, however, when a 

 shell was disturbed it fell off and left the cast in 

 my hands. I learned many things about this 

 great exposure. All the various rocks show they 

 have been laid down under water. I can 

 imagine a great flood plain along the cretaceous 

 ocean at first, just below the surface of the 

 water, that must have been brackish at first for 

 so many oyster shells to accumulate. There were 

 no great reed and rush covered plains where the 

 horned dinosaurs could feed; no bayous or lakes 

 bordered with dense jungles of vegetation, where 

 countless swimming duckbills enjoyed the lux- 

 urious feeding places, but a shallow waste of wa- 

 ters, where oysters secured a precarious foot- 

 hold. Then the scene changed. The land was 

 raised sufficiently so a rank vegetation of sponge 

 moss and other forms covered all the rising 

 land until a vast bed of vegetable matter had ac- 

 cumulated, when it went below the sea and was 

 covered with ocean mud and eventually com- 

 pressed into coal. Then again the land was lift- 

 ed above high tide, fresh water for many years 

 spread out in shallow sheets over the region in 

 which there was sufficient moss and other vege- 

 tation to provide food for the univalves or gas- 



