68' The Saint Peter Sandstone. 



An intermixture of argillaceous bands has been described 

 (21) from northeastern Wisconsin; such an intermixture is 

 generally found at the upper and lower limits of the forma- 

 tion. But, the Saint Peter Sandstone proper is a pure, 

 friable, white rock with very little impurities. It i& 

 thoroughly pervious to water, so much so that a small 

 stream poured upon the surface of a slab readily goes 

 through it. 



STRUCTURE. 



Ordinarily the clear whiteness of the sandstone conceals 

 its structure; on the other hand the infiltrated colors bring 

 it out the more strongly. Stratification is always discern- 

 ible often with fine lamination, crossbedding, and assorted 

 layers of coarse and fine material. Transverse fissures also 

 occur. 



PALAEONTOLOGIC CHARACTERS. 



Discovery of Fossils. 



Owing to the friability of the rock and the total absence 

 of shells, fossils are difficult to find. James Hall writes i» 

 1862, (loc. cit.) that ''no vestige of an organism has been 

 observed" and "it is not probable that such remains will be 

 found." Some years afterwards, however, N. H. Winchell 

 (17.) reported shells of a Lingulepis from the top shaly 

 strata of Saint Peter at Fountain, Fillmore county, Minne- 

 sota. T. C. Chamberlin (21 and 26) found worm burrows 

 and fucoids near Beloit and Waterloo, Wisconsin, and these 

 are reported by him to be not entirely in the uppermost 

 strata of the formation. 



Joseph F. James (34 p. 126) reports that he visited 

 Fountain, Minnesota in 1889 and collected specimens of the 

 Lingulepis and an Orthis. I have myself later collected the 

 same and some other species at that locality in the described 

 upper shal}^ strata. Species have been collected from similar 

 strata near Dodgeville, Wisconsin. These fossils are all from 

 the transition strata at the fop of the formation, i. e. at the 

 base of the Trenton. 



Several species do occur in the body of the formation. 

 As a student working under the direction of Professor C. W. 

 Hall, I found in the year 1890, a large fauna in the Saint 



