178 Vlrioh — Chattanoogan Series with Special Reference 



Between Cleveland and Sandusky there should be a point 

 where the Chagrin is practically absent and where, therefore, 

 the shale complex, minus the Bedford, is made up wholly of 

 the Cleveland, Olmsted, and such part of the presumably like- 

 wise overlapping Huron as may have reached there. This 

 place would seem to be near the mouth of the Vermilion 

 where Newberry* reports a well as showing "the thickness of 

 the shales which separate the Berea grit from the Sandusky 

 (Delaware) limestone to be less than 400 feet." 



The foregoing interpretation of the relations of the Chagrin 

 and the Huron (see also figs. I— III, p. 166) will seem less strange 

 when it is remembered that decided changes in the direction of 

 marine invasions occurred also at other times in the areas under 

 discussion during the Silurian, Devonian and Waverlyan. Thus 

 it may be said to be established that the Onondaga invaded 

 from the south while the late Devonian faunas came in chiefly 

 from the east, only one of the latter, the Lime Creek fauna of 

 Iowa, having extended eastward to New York from the west. 

 Further, it seems undeniable that all of the Chattanoogan 

 black shales came in from the south while the Bedford prob- 

 ably invaded Ohio from the southeast. In other ages finally 

 Atlantic seas that transgressed westwardly or northwestwardly 

 across eastern and northern Ohio alternated with seas that came 

 in from other oceanic basins, and advanced in approximately 

 opposite directions. Such oscillations and resulting changes in 

 direction of marine transgression in the continental basins are 

 really of very common occurrence in geological history. 



dossil evidence. 



Finally a few words concerning the faunal aspects of the 

 Chattanoogan shale problems. As I have already said in re- 

 marks following the preceding description of the formations 

 involved in this discussion, it seems unnecessary to enlarge on 

 the fauna of the Chagrin formation. After saying, as all 

 have who have studied its fossils, that they can not be older 

 than Portage and are most probably Chemung, it might be 

 sufficient to add that under the stratigraphic arrangement here 

 proposed the Chemung affinities of the Chagrin fauna may 

 justly be emphasized. But I shall further add that the prob- 

 able presence of an unquestionable species of Syringothyris 

 in the upper part of the formation,! if it is used at all, must 



* Geol. Survey Ohio, vol. ii, p. 216, 1874. 



f The occurrence of Syringothyris in the Ohio section beneath the Cleve- 

 land has recently been denied. However, some well-preserved specimens of 

 a new species of this genus, collected near Jefferson in Ashtabula County, 

 from beds regarded as older than the Cleveland by such good authorities on 

 Ohio stratigraphy as Professors H. P. Cushing and Charles S. Prosser (in- 

 formation contained in letters to the writer) seem to revive the asserted 



