INTRODUCTION. 103 



an elevation of 1,450 feet above the sea on the nor-th side of the rivei* 

 a somewhat slidden hillside shows, to a height of thirty feet, a scarped 

 face of dark grey clay shales, representing a" hoi'izon very near the base 

 of the Pierre formation. Thirty-five feet higher up the bank, and on 

 the south side of the river, is an outcrop of light grey hard siliceous clay 

 shale, associated with a few dark nodules of ironstone. Specimens of 

 this shale were collected and brousrht to the Museum of the Geological 

 Survey at Ottawa, and on being submitted to a microscopical examina- 

 tion were found to contain large numbers of well-preserved Kadiolai-ia, 

 preliminary notes of the occurrence of which were published in the 

 American Journal of Science and Arts for September, 1890, page 230, 

 and in the Transactions of the Royal Society of Canada, 1890, Section 

 TV, page 1 1 3. 



Immediately on learning of the discovery, Dv. D. Riist, of Han- 

 over, Germany, the most noted living authority on these minute fossil 

 forms, kindly consented to examine and determine any species that he 

 might be able to find in this clay shale, and the following report is the 

 result of his laboui-s. 



Above this outcrop of Radiolarian shale no exposures of rock in 

 place were seen, but the position assigned to it, near the base of the 

 Pierre, is believed, from the evidence of numerous other exposures, to 

 be approximately correct. 



J. B. TYRRELL. 



