38 CHAZY GROUP. 



in North-eastern Iowa and the eastern part of Minnesota, where its dip is westerly. 

 It occurs in Illinois, at Oregon, on Rock River, and at La Salle, on the Illinois, 

 caused by a local uplift. The unevenness of the Calciferous bed, as proven by 

 artesian boring, is greater near the margin or shore-line of the oceanic deposit than 

 elsewhere. It is known, by artesian boring, in Minnesota more than 100 miles 

 from the Mississippi, and in Illinois more than 100 miles from its exposure in Wis- 

 consin. In some places the sand mingles with the calcareous materials and forms 

 passage beds to the Trenton, and at other places the transition, while conformable, 

 is abrupt. In Missouri the upper part of the Group received the name of the 

 "First Magnesian Limestone," and the lower part the "First Sandstone" and the 

 " Saccharoidal Sandstone." The latter presents very few characters not found in 

 the exposures in Illinois and Wisconsin ; while the former is limited in its distribu- 

 tion, and indicates local changes in the deposition of the upper part of the Group. 

 It is usually a gray or buff crystalline, cherty, magnesian limestone, filled with 

 silicious patches, breaking readily with the hammer, and extremely variable in 

 thickness. In New Jersey it consists of a fine, even-grained limestone, sometimes a 

 pure dolomite, except near the base, where there are sandy and calcareous layers. 

 It occurs in long, narrow belts, in a north-east and south-west direction, correspond- 

 ing to synclinal and anticlinal axes. From this State and from Pennsylvania it is 

 exposed in numerous places within the Appalachian System as far south as Ala- 

 bama, and may generally be detected by the presence of Maclurea magna. In Ten- 

 nessee the lower part is an argillaceous limestone, varying in thickness from 50 to 

 600 feet; and if the marble of Knox County is referred to it, its upper part 

 will have a thickness of more than 400 feet. It occurs in the Wahsatch Range in 

 Utah, in the White Pine district of Nevada, in the Wind River Mountains of 

 Wyoming, and in numerous other localities in the great system of mountain ranges 

 of the West, where it also bears the name of the Quebec Group. It has been 

 identified in the Arctic regions, on King William's Island, North Devon, and Depot 

 Bay, in Bellotis Strait, where it is a dolomitic limestone. It graduates into the 

 Black River wherever the latter is separable from the Trenton, and especially 

 where the Birdseye limestone is present. Numerous fossil species connect it inti- 

 mately with the overlying rocks, many of which occur as high as the Hudson 

 River, viz. : Strophomena altemata, S. incrassata, Orthis perveta, Leperditia canadensis, 

 L. kwckana, L. amygdcdina, Orthoceras multicameratum, 0. bilineatum, and Modiolopsis 

 nasuta. The most characteristic fossil is Madurea magna. 



