lOO ILLINOIS ACADEMY OF SCIENCE. 



From this exposure in the Cady quarry the section may be con- 

 tinued upward in the Mill Creek outcrops, of which the lowest 

 member, E^a, corresponds to the upper portion of the member 

 N2J ; and members Eib and Ejc to the member N2k. 



The sections along Mill Creek comprise some of the most 

 typical exposures of the Devonian rocks found in Rock Island 

 county. With the exception of the section obtained in the Cady 

 quarries, the Mill Creek sections, taken in their entirety, show the 

 greatest thickness of Devonian strata, and, without exception, 

 yield the greatest number of fossils. 



The sections begin near the confluence of Mill Creek and Rock 

 River, where the Fayette breccia appears, and extend continu- 

 ously to the center of Sec. 25, T. 17 N., R. 2 W. A total vertical 

 thickness of more than sixty feet of limestone is exposed in this 

 section. A number of outcrops occur farther up the stream, but 

 the strata exposed are included within the continuous section far- 

 ther down the stream. The Mill Creek section marked E^ is as 

 follows : 



SECTION OF STRATA EXPOSED ALONG MILL CREEK. 



Feet. In. 

 Eip. Layer of gray, shelly, somewhat crystallized limestone, con- 

 taining a large number of small shells of Atrypa reticu- 

 laris ; I 3 



Zaphrentis sp. Schisophoria striafula 



Zaphrentis gigantea Reticularia Htnbriata 



Athyris fultonensis Spirifer iowensis 



Atrypa reticularis Spirifer subvaricosus 



EiO. Coral limestone; Acerviilaria davidsoni coral reef 2 6 



Ein. Brown limestone extending up to the top of the Acerviilaria 



coral reef • 4 



Striatopora rugosa Atrpa reticularis 



Cyclotrypa communis Chonetes scitulus 



Cystodictya hamiltonensis Crancena iozvensis 



Euspilopora barrisi Cyrtina umbonata^ 



Fenestella vera Pentamerella diibia 



Fistulipora monticulata Spirifer subvaricosus 



Hemitrypa tenera Spirifer euryteines 



Orbignyella tenera Spirifer iowensis 



Reteporina hamiltonensis Stropheodonta demissa 



Semicoscinium rhombicum Stropheodonta perplana 



Platyceras sp. 



Eim. Brown, fine-grained somewhat crystalline and crinoidal lime- 

 stone, weathering into slabs 2 to 3 inches thick, and yield- 

 ing the following fossils ; • 5 



Eridotrypa appressa Schuchertella chemungensis 



Atrypa reticularis Spirifer euryteines 



Crancena iowensis Spirifer iowensis 



Gypidula comis Spirifer subvaricosus 



Reticularia Umbriata Stropheodonta demissa 



Schizophoria striatula Stropheodonta perplana 



Phacops rana 



