CHAPTER II. 
LOCAL SECTIONS ON THE UPPER MISSISSIPPI. 
a. Above the Mouth of the Wisconsin.—For the purpose both of investigating the 
mineral contents of the Lower Magnesian Limestone and Lower Sandstone of Wis- 
consin, Iowa, and Minnesota, and at the same time tracing out the elements of 
stratification of these formations, and their palzeontological details, I was instructed 
to make minute local sections, at various points in the Valley of the Mississippi, the 
results of which are contained in this chapter. 
My observations commence at the Falls of St. Anthony, where F. 2, c, forms the 
base of the sections capped with the shell-beds of F. 3, A. 
On the east side, the different members of that formation occur in the following 
order, above the white sandstone. 
Feet. 
1. Grayish buff-coloured layers of Magnesian limestone, containing 
numerous casts of Leptena, Terebratula, Orthis, Spirifer, Ortho- 
ceratites, Pleurotomaria, &e., ; : ; F 6 
2. Ash-coloured argillaceous limestones, in thin layers, containing 
but few fossils, . ; ; : : : ; ; 5 
3. Highly fossiliferous shell limestone, of a bluish-gray colour, i é 23 
From three to four feet of the upper beds of the section are above the top of 
the cascade. The whole height of the perpendicular fall is sixteen feet. 
Many of the organic remains of the upper bed are identical with the Trenton 
limestone, Utica slate, and Hudson River group of the New York system, and their 
western equivalent, the blue limestone of the Ohio Valley. 
The most characteristic species in these beds are Leptena alternata, L. planum- 
bona, L. sericea, Orthis testudinaria, O. tricenaria, O. disparilis, Terebratula modesta, 
Atrypa capax, Bellerophon bilobatus, Pleurotomaria lenticularis, P. subconica, P. um- 
bilicata, Orthoceratite (species undetermined), Calymene senaria, Isotelus gigas, Lichas 
trentonensis(?), Ceraurus pleurexanthemus, Cheetetes lycoperdon. 
About a quarter of a mile below the cascade, the lower beds of the shell lime- 
stone are better exhibited than at the last section, and they rest here on the white 
sandstone (F. 2, c). The section is as follows: 
