MurcliS, 18G9.] ^^ [Winchell. 



ON THE GEOLOGICAL AGE AND EQUIVALENTS OF THE MARSHALL 



GKOUP. 



By Prof. A. Winchell. 



Contents. 



I. The existence of controversy. 

 II. History of discovery and opinion. 

 III. Present state of our stratigrapliical knowledge. 

 Tables of stratification in various States. 

 Parallelism of these strata. 

 The Black Shale. 



The Carboniferous Conglomerate. 



The strata between the Conglomerate and the Waverly series. 

 The Waverly series and its equivalents. • 

 Not synchronous with Portage and Chemung. 

 Huron Group synchronous with Portage and Chemung In Michigan, 



Ohio, Kentucky, Iowa. 

 This synchronism consistent with the tenor of Geological History. 



TV. Present state of our paleontological knowledge. 



Characters and parallelism of the Huron Group. 



Catalogue of fossils from the Marshall Group and its equivalents. 



Discussions of the catalogue. 



Relations of Western localities among themselves. 



Eelations of these to Portage and Chemung. 



Kelations of the same to Conglomerates of western New York. 



T. The Fauna of the Marshall Group presents a Carboniferous aspect. 



Fossils identified with Carboniferous species of America and Europe. 



Fossils whose analogies recur in Carboniferous rocks. 



Generic and subgeneric types of a Carboniferous character. 

 TT. The Fauna of the Chemung Group presents a Devonian aspect. 

 yil. Can the Marshall and Chemung Group be synchronized ? 



Keliability of fossils in determining parallelism. 



The Marshall and Chemung cannot be synchronized. 



Influence of geographical conditions. 

 YIII. Parallehsm of the Catskill and Marshall Groups. 



Objections considered. 



Paleontological affinities of tlie two. 



Table of geological equivalents. 

 IX. Their names. 



Appendix. Keferences to publications on the subject. 



I. Existence of Controversy. 

 Every person conversant with the history of American geological science 

 is aware of the controversy which has long existed in reference to the age 

 and equivalents of the strata lying between the Corniferous limestones and 

 the limestones of the Lower Carboniferous system. Geologists of the 

 highest ability — both American and European — have participated in the 

 discussions ; and western geologists, almost without excei)tion, have been 

 constrained to commit themselves, for specific reasons, to definite, though 

 often diverse, views in reference to the geology of the zone in question. 

 As additional facts have been successively brought to light, some important 

 progress has been made in the settlement of controverted points ; and the 

 great body of western geologists seem to have united with considerable 

 unanimity in a judgment upon the main issues. Very persistent oppo- 

 A. P. S. — VOL. XI — H 



