172 THE CAMBRIAN. [bull.81. 



stone of the Wisconsin River. 1 Five years later, in the report of a 

 geological reconnaissance of the Chippewa land district of Wisconsin, 

 he describes with considerable detail Formation 1, or the lower sand- 

 stone of the Upper Mississippi. The formation, as a whole, is subdi- 

 vided into five parts. The lowest part rests upon crystalline and 

 metamorphic roeks, in the eastern part of the Chippewa land district, 

 as a coarse sandstone overlaid by a still coarser quartzose sandstone. 2 

 At the Falls of the St. Croix the schistose, silico-calcareous layers of 

 the second division are highly fossiliferous. In the third division the 

 prevailing genera are Lingula and Orbicula 3 and it is designated as 

 the "Lingula sandstone." In speaking of the beds of sandstone 

 beneath the fossiliferous layers at Mountain Island it is stated that in 

 all probability this is the western equivalent of the Lingula beds of the 

 New York Potsdam sandstone. 4 



A notice of the discovery of the fauna in the lower sandstone of Wis- 

 consin was communicated by Dr. Owen in 1848 to the Geological So- 

 ciety of France through a letter to M. de Verneuil. 5 



In a letter descriptive of the geology of southeastern Wisconsin ad- 

 dressed to Mr. J. W. Foster, Mr. I. A. Lapham states that — 



The Inferior, or Potsdam sandstone, is found at Janesville and above, occupying the 

 bed of the river. The grains are rounded, smooth, and without apparent cement ; 

 the rock easily crumbles upon exposure ; color white or red. The white variety 

 might be used for the manufacture of glass. The discovery, in 1849, of that singular 

 and characteristic fossil described by Mr. Hall as Scolithus linearis (New York Pal., 

 vol. 1, p. 2) in this rock, in Sauk County, may be considered as settling the question 

 of the identity of this rock with the Potsdam sandstone of the New York reports. It 

 occupies much of the counties Marquette and Columbia, enters Dane County, and is 

 seen in the banks of Rock River from Lake Koshkonong to Janesville. 



* * * II. Calciferous rock of Eaton. — Resting immediately upon the sandstone, 

 at Janesville, is a limestone with grains of the same sand intermixed, giving it the 

 form and appearance of an oolite limestone ; the amount of sand diminishing as you 

 rise from the surface of the sandstone. It ajpeords exactly with the description given 

 of a portion of the calciferous sandstone of New York, and contains the same fucoid 

 (Palceophyew tubularis), as well as other characteristic fossils. Its character and rel- 

 ative position also clearly show that it is the same rock that, farther west and north, 

 is called the Lower Magnesian limestone, by Drs. Owen and Locke.« 



In the same report, Mr. Charles Whittlesey describes the sandstone as 

 it occurs near Wolf Eiver, etc., stating it to be a sandstone easily 

 crushed between the fingers, which has been so extensively denuded 

 that it is only here and there that a trace of its former existence is 



1 On th6 geology of the Western States. Am. Jour. Sci„ vol. 45, 1843, p. 164. 



2 Owen, David Dale: Report of a geological reconnaissance of the Chippewa land district of Wis- 

 consin, and incidentally of a portion of * * * Iowa and of the Minnesota territory. Letter of the 

 Secretary of the Treasury communicating a report of a geological reconnaissance of th«. Chippewa 

 land district of Wisconsin, etc., by D.D. Owen, Thirtieth Congress, first session, Senate Ex. Doc. No. 

 57, 1848, p. 13. 



3 Op. cit., p. 14. 



4 Op. cit., p. 15. 



* Letter on geology of Wisconsin Territory. Bull. Soc. geoL France, 2 e ser., vol. 5, 1848, pp. 294-296. 



6 Lapham, L A. : "On the geology of the southeastern portion of the State of Wisconsin, being the 

 part not surveyed by United States geologists." Rept. on the geology of the Lake Superior laud dis- 

 trict, by Foster and Whitney, part 2, 1851, p. 169. 



