572 PROCEEDINGS OF THE SAINT LOUIS MEETING 



Calvin at one time gave it as 40 feet,* but later gave it greater, f Bain, with 

 Calvin's earlier view, made it 50 feet. ± 



White and Saint John wisely refrained from adopting Hayden's names and so 

 avoided the error. \ 



C. The Greenhorn limestone is closely equivalent to the Inoceramus beds of 

 White, and has been unfortunately confused with the Niobrara from the first. 

 This limestone and its associated chalk abound in Inoceramus labiatus, which fossil 

 occurs in the Graneros, but in the Carlisle and Niobrara gives place to I. deformis. {?) 



D. The dip of the formation is generally slight and toward the north. Observa- 

 tions of the top of the Benton show it to be about 1,380 in northern Union county, 

 South Dakota, and 1,300 about Mitchell ; but there is also a dip eastward with the 

 general slope of the country, so that about Marshall, Minnesota, it is about 1,100. 

 Near Milbank it is about 1,100, but at White Rock, near the north end of lake 

 Traverse, it is considerably lower. 



Correction of former Interpretations 



1. The main error, videlicet, mistaking the Greenhorn chalky limestone for the 

 Niobrara, was first made by Hayden and Meek, and later students simply accepted 

 and continued it. This is evident from the following quotations: 



Doctor Hayden says the Dakota " is succeeded by a series of black, plastic, lam- 

 inated clays, with light-colored arenaceous partings and thin layers of sandstone. 

 Near the mouth of the Vermilion river the upper portion becomes more calcareous 

 and gradually passes into the next group." || 



He also says, in the table which has been so much copied, that the Niobrara 

 "ranges in bluffs along the Missouri below the Great Bend to the vicinity of the 

 Big Sioux river; also below there on the tops of the hills. "f And more definitely 

 in 1872, that the Niobrara, "chiefly limestone, almost entirely composed of the 

 shells of a species of Inoceramus," appears in the hills near the north limit of the 

 Omaha reservation.** 



Meek, who first outlined the present classification of Cretaceous rocks of this 

 region in 1856, ft continues this view in Hayden's Final Report, volume ix, page 



XXV. 



White and Saint John, as already stated, avoided the error by not adopting Hay- 

 den's names,U but Calvin attempted a harmony and fully accepted the mistake, 

 and, moreover, adopts it as a basis for a theory concerning the origin of Cretaceous 

 formations.^ He, however, acknowledged his error after finding Prionocyclas in 

 the shales above his supposed Niobrara. Bain,|||| and also the writer, followed the 

 same error for a time. 



2. Another error followed logically from the first, videlicet, that there is a syncline 



* Iowa Geol. Survey, vol. i, 128. 



t Ibid., vol. x, p. 114. 



X Ibid., vol. iii, p. 110, 1893. 



§ Geol. of Iowa, vol. 2. 



|| Second Ann. Report U. S. Geol. Survey of Terr., 1870, p. 90. 



H Ppoc. Acad. Nat. Sci., Phila., 1861. 



** Final Report on Nebraska, 1872, p. 42. 



ft Am. Acad. Arts and Sci., Boston, vol. v, p. 405. 



ft Geol. of Iowa, vol. i, p. 274, 1870. 



§§ Am. Geolos^ist, vol. ix, p. 304, quoted largely; Iowa Geol. Survey, vol. i, p. 129, 1892. 



Illl Iowa Geol. Survey, vol. v, p. 275 ; also vol. viii, p. 331. 



