^iamb.) FIRST MINNESOTA REPORT. 167 



ie Spergen Hill fossils found at Bloomin^ton, Iud., at about the bo- 

 son of the Lower Carboniferous series, are miniature representatives 

 known larger species, belonging for the most part to the genera of 

 'orals, Blastoidea, Brachiopoda, etc. They are crowded, together in 

 imense numbers, but finely preserved, in this locality, and a few have 

 >en found at the same horizon in Illinois, Iowa, and Missouri, but 

 lone in such numbers, or in any locality west of Missouri or Iowa, until 

 Mr. Meek discovered hundreds of these little fossils in a small, dark- 

 gray mass of crumbling limestone, brought by Professor Bradley from 

 Idaho. The fossils belong to about 17 species of the same genera found 

 at Spergen Hill, and of the species about one-half were uudistinguish- 

 able from the Spergen Hill forms. 



In the first annual report of the Survey of Minnesota 1 a chart 2 is pre. 

 sen ted with some modifications in the classification and correlations of 

 the Missisippian series. 



The Carboniferous system is represented on the chart, although noth- 

 ing representing it is recorded for Minnesota, and is divided into the 

 following groups : 



Permian. 

 Coal Measure. 



Carboniferous conglomerate. 

 Subcarboniferous. 



The Subcarboniferous group is made up as follows for North America: 



f Chester limestone. 



,-*,. • ■ • c _, .• ; St. Louis limestone. 

 Mississippi formation { 



. Keokuk limestone. 



I Burlington limestone. 



Subcarboniferous. 



^Marshall formation. .. .Marshall sandstone. 



The " Mississippi formation " is the equivalent of the " Mountain 

 limestone " of Europe and Tennessee. 



The " Marshall formation " is the equivalent of the " Kinderhook " of 

 Iowa and Illinois and of the " Old Red sandstone n of Europe. 



The Devonian system is made up as follows : 



System. Groups. Formations. Strata of North America. 



iron shale. 



f Hamilton Hamilton. 



lton limestone. 



^ Hiiroi 



i / 



V Hami 



Devonian .. ■! Corniferous. . S Corn iferous limestone. 



I Upper Helderbergi I °»°»^ limestone. 



~ . , Schoharie grit. 



V Onskany J „ . ... 



\ Cauda-galli grit. 



I Oriskany sandstone. 



The usage of " Mississippi " as a name for the limestones of the Sub- 



1 The Geological and Natural History Survey of Minnesota, by N. H. Winchell, State Geologist, 

 1873. 



% Chart of geological nomenclature, intended to express the relation of Minnesota to the great geo- 

 logical series of the earth, and the probable equivalency of some of the names the formations have 

 received in the various States and in Europe, opp., p. 40. 



