THE CRETACEOUS RIM OF THE BLACK HILLS. 25 I 



resented than in the following figure copied from Professor 

 Newton's report :^ 



At that date the opinion widely prevailed that there was no 

 Lower Cretaceous in North America. The Shasta, Kootanie, 

 and Comanche groups were unknown, the Potomac of Virginia 

 was supposed to be "Upper Oolite," and the Iron Ore Clays of 

 Maryland and Plastic Clays of New Jersey were classed as Weal- 

 den and referred to the Jurassic. Meek and Hayden had 

 been unable to find any Cretaceous deposits lower than No. i of 



Fig. I. — Ideal section across Red Valley on Amphibious Creek. 

 I. Carboniferous. 



Red sandstones and clay (Red Beds). 

 Purple limestone (Red Beds). 

 Red clay with gypsum (Red Beds). 

 Jura. ' 



Cretaceous sandstone capping the foot-hills. 



their famous section, and this was believed to be the oldest Cre- 

 taceous deposited on this continent, which was supposed in some 

 way to have been out of water during the entire period that sep- 

 arated this from the Jurassic. 



My attention was first attracted to the Black Hills by a letter 

 received at the Smithsonian Institution in February, 1893, from 

 a resident of Hot Springs, South Dakota, inclosing photographs 

 of certain petrifactions found in that vicinity which he said had 

 been called "Cycads." The letter and photographs were 

 referred to me on the presumption that these objects were of 

 vegetable origin. I at once perceived that they were fossil 

 cycadean trunks closely resembling those collected by Tyson in 

 i860 in the Iron Ore Clays of Maryland and named by Professor 

 Fontaine Tysoiiia Marylandica, and, therefore, also similar to the 

 forms found by Mantell and others in the early part of the cen- 

 'Geol. Black Hills of Dakota, p. 141, fig. 20. 



