XXX THE PALEONTOLOGY OF MINNESOTA. 



less dolomitic, with alternations of shale and of Blue limestone. Receptaculites is confined 

 to the Galena limestone, within the mineral district, but further north, as on Turkey and 

 Upper Iowa rivers, it is abundantly scattered through the shaly beds of the Blue. 



The Hudson River shales contain from one- tenth to one-fifth of their weight of carbon- 

 aceous matter, " The Hudson River shales, with the closely allied Hudson River slates, 

 seem to have been deposited under conditions somewhat resembling those under which the 

 true coal-bearing rocks were accumulated." 



Henry D. Rogers. 



1858. The Geology of Pennsylvania, a government survey. By HENRY DAK WIN 

 ROGERS. Vol. II, Philadelphia, 1858. 



In the discussion of the history of the Matinal period (p. 784), the author makes a sugges- 

 tion, carried out more fully by Mr. C. D. Walcott in 1879, that the Galena limestone oc- 

 cupies nearly the same stratigraphic position as the Utica slate of New York. He adds: 



"But whether it was produced in the same age with that deposit, or in that next before it, or, 

 again, in that next after it, we are without the means, for the present at least, of ascertaining, since the 

 black slate and it nowhere occur in the same districts, nor even approach each other by a wide geograph- 

 ical interval. ****** The very marked transition between the Matinal argillaceous limestone 

 [Trenton] and this lead-bearing rock, in regard to their organic remains, strongly intimates that some 

 important physical change took place in the interval." 



It is evident, from the last remark, that Prof. Rogers considered, at that date, the 

 lead-bearing rock as a part of the Cliff limestone, as stated by Hall. This idea, however, 

 had been corrected prior to the publication of the Pennsylvania report, largely through 

 the agency of Prof. Hall, in the report of Foster and Whitney (1851), though perhaps not 

 prior to the time at which Prof. Rogers wrote the above words. At any rate, as a matter 

 of fact, there is no great contrast in their organic remains, between the Trenton limestone 

 and the lead-bearing rock. The contrast which Prof. Rogers refers to as obtaining 

 between the Matinal limestone and the Cliff (Niagara) to which the lead-bearing rock 

 had been referred by Owen and Hall, as those formations are represented in New York 

 and Pennsylvania, is that which is now well known at the top of the Galena. 



Edivard Daniels. 



1858. Annual Report of the Geological Survey of the State of Wisconsin, for the year 

 ending Dec. 31, 1857. By PROF. E. DANIELS, Madison, 1858. Pamphlet of 62 pages. 



The author, in describing the iron ore at Iron ridge, Dodge county, reverts to the fact 

 that he made the discovery of the "Blue shale" in 1851, and described it as "Nucula shale" 

 in 1853. He evidently is in error when he states (p. 13) that this stratum had been 

 ' 'recognized by -Prof. Hall in Poster and Whitney's report on the Lake Superior Land 

 district as belonging to the Hudson River group," since it was only in the Green bay 

 region, in the eastern part of the state, that Prof. Hall recognized the Hudson River 

 formation, and there was then no known connection of the Blue shale of the Mississippi 

 valley with the Hudson River strata seen in the region of Green bay. This connection 

 was pointed out by Dr. Percival. 



