122 Wisconsin Academy of Sciences, Arts, and Letters. 



the calciferous formations of the Upper Silurian age of rocks, as 

 exhibited in the vicinity of Milwaukee. 



Prof. Hall, also in his statements in Vol. I, Greology of Wiscon- 

 sin, represents the strata of rocks lying above the Niagara, as the 

 equivalent of the Salina or Onondaga Salt group of New York, 

 or the Guelph, or Gault, of Canada, and the Le Claire, of Iowa. 

 Notwithstanding, he was unable to trace the characteristic fossil, 

 Eurypterus remipes of the Water-Lime G-roup. Similar views are 

 expressed by him in his prefatory remarks in his paleontology of 

 Wisconsin, also see Paleontology of New York, Vol. III. Like- 

 wise what are called, on page 72, Vol. I, Geology of Wisconsin, the 

 upper Helderberg and Hamilton groups, have proved to be what is 

 "tJ^ology of jthe Hamilton cement, of Devonian age, in Vok-ifruf 

 now termed W'iscansin,- ;«•. :^ '';/, '•/ v: ' ..-.■•■- 



An analytical examination ot the expressed sentiments of the 

 authors in Volumes first and second of Geology of Wisconsin, con- 

 cerning the lithological character of the rocks containing the fauna 

 of Wisconsin, especially its eastern portion, shows no very marked 

 distinction or discrepancy, for their final summation respecting 

 the area, the age, and periods, embracing the characteristic epochs, 

 as generally admitted in American Geology. 



To the general student of Natural History, the previous class- 

 ification established by Hall, on 447 page, of Vol. I, of Geology 

 of Wisconsin, comprehensively covers the synonymous terms of 

 Mayville and Byron beds, and upper and lower coral beds, lying 

 below the Waukesha limestone. For the Hamilton cement, the 

 Le Claire, the Eacine and Waukesha limestones, embrace all the 

 fauna belonging to that portion of the Upper Silurian, equivalent 

 to the Salina, Lower Helderberg and Hamilton. 



Such an increase of synonyms has a tendency to embarrass 

 the student in his study of paleozoic life, notwithstanding. Prof. 

 Charaberlin, while reiterating the ideas advanced by Prof. Hall, has 

 invested them, in a fuller and more interesting phraseology. But 

 some facts concerning the quarries in Milwaukee county do not sub- 

 stantiate the correctness of Prof. Chamberlin's views, that the three 

 classes of limestone, Mayville, Waukesha and Eacine, lying above 

 the Trenton period of rocks, were formed simultaneously. 



