193 ILLINOIS STATE ACADEMY OF SCIENCE 



In volume I. of the reports on the Geological Survey of 

 Illinois Worthen" referred the Devonian limestones of Rock 

 Island County, Illinois, to both the upper Helderberg 

 (Onondaga) and the Hamilton formations. In discussing 

 the Geology of northeastern Iowa in 1891 MaGee^ con- 

 sidered the Devonian limestones as a unit and revived the 

 name "Cedar Valley limestones" applied by Owen to these 

 strata more than 40 years before. MaGee proposed to dis- 

 tinguish the lower, brecciated member of these limestones 

 as the "Fayette breccia" from the town of Fayette, Iowa, 

 where they are well exposed. 



The same year Calvin^ gave the name Gyroceras beds 

 to the strata a few feet in thickness lying immediately above 

 the brecciated limestones containing many Gyroceroid 

 shells. 



In 1895 Norton^o proposed the name Wapsipinicon lime- 

 stone for the Devonian strata included in the Fayette brec- 

 cia of MaGee, and the Gyroceras beds of Calvin, from the 

 Wapsipinicon River in eastern Iowa where these rocks 

 are well exposed. He restricted the name Cedar Valley 

 limestone to the more shaly and very fossiliferous strata, 

 that occur above the Gyroceras beds in eastern Iowa. 

 Norton^i also divided the Wapsipinicon limestone into the 

 following members: Otis beds at the base; Kenwood 

 shale; Lower Davenport limestone, equivalent to the 

 Fayette breccia of MaGee; and Upper Davenport lime- 

 stone, corresponding to the Gyroceras beds of Calvin. 

 This classification has generally been followed by the Iowa 

 Geological survey. Weller^^ has considered the Wapsipini- 

 con limestone of Iowa in the main equivalent in time to the 

 later Hamilton of the New York section and the Cedar Val- 

 ley limestone about contemporaneous with the Portage 

 group of New York. 



The writer^^ has recently correlated all of the Cedar Val- 

 ley and Wapsipinicon limestones of Iowa and Illinois about 



7 Worthen, A. H., Geol. Surv. of Illinois, Vol. 1, p. 120, 1866. 



8 MaGee, W. J., Eleventh Ann. Kept. U. S. Geol. Surv., p. 319, 1891. 



9 Calvin, Samuel, Am. Geologist, Vol. VIII, p. 142, 1891. 



10 Norton, W. H., Iowa Geol. Surv., Vol. IV, p. 155, 1895. 



11 Norton, W. H., Proc. Iowa .\cad. of Science, Vol. I. pt. 4, pp. 22-24, 1893. 



12 Weller, Stuart, Outlines of Geological History with Especial Reference to 

 North Am., p. 101, 1910. 



13 Savage, T. E., Devonian Formations in Illinois, Am. Jour, of Science, 4th 

 Ser., Vol. 49. Mch., pp. 181 and 182, 1920. 



