FOSSILS OF THE NIAGARA GROUP. 349 



more distiactive character ou the Mississippi River, it seems necessary to elevate 

 them to the same rank as the other groups of the series." 



Some two or three years later I explored the geology of the central 

 and eastern portions of Wisconsin and the adjacent parts of Illinois. I 

 here found the limestone of Racine, and a part of Waukesha and some 

 other localities, resembling in all respects that of Leclaire and holding 

 many of the same fossils. It is likewise underlaid by the even-bedded 

 darker-colored limestone, bearing Haly sites catenulatus, Pentamenis oUongus^ 

 and many large Orthoceratites, which are everywhere regarded as evidence 

 of the Niagara age. I could not hesitate, therefore, to parallelize the suc- 

 ceeding beds with the limestone of Leclaire, though we had failed to trace 

 that formation across the country in a continuous outcrop. At the same 

 time, on critical examination of the collection of fossils made at Racine and 

 at some other points, I detected many species known as characteristic of 

 the Niagara formation in the State of New York, requiring its recognition 

 as a member of that group (rather than of the Onondaga salt group), 

 and uniting with it as identical in position the Leclaire limestone.* 



At the same time, we have recognized from Racine and adjacent 

 localities, including Leclaire in Iowa and a single locality in Illinois, the 

 following species which are identical or very closely allied to those from 

 Gait in Canada West: Pentmnerus occidentalism an Obolus-Yike fossil a 

 Favosites and a species of Amplexus which are identical in several locali- 

 ties, Cyclonema sulcata, Murchisonia logani, Murchisonia identical or closely 

 allied to M. mylitta, Billings, an undescribed Murchisonia from Racine 

 identical with one from Gait, Subulites ventricosa, Pleurotomaria solaroides ? 

 Loxonema longispira, besides other forms which are closely allied to species 

 of the Guelph limestone. 



An examination of several localities in Wisconsin shows that this peculiar 

 fossiliferous limestone is very unequally distributed. At Racine it has a 

 very considerable thickness ;t while in other places, either from denuda- 

 tion or other causes, it is very thin, or even absent. In some places in 

 thQ vicinity of Milwaukee and Waukesha, there are indications of beds 

 of passage from the regularly bedded limestones below to the unequally 

 bedded rock above. There appears indeed very good evidence of the 

 irregular or unequal accumulation of this higher rock in many of the locali- 

 ties along a considerable portion of the outcrop ; and where the lower 



* Report on the Geology of Wisconxin, p. 67. 1861. 



1 1 am inclined to believe that I have over-estimated the thickness of the limestolie at Leclaire 

 from the presence of Jines of false bedding, but I have had no opportunity of a reexamination of 

 the locality. 



