An Account of the Middle Silurian Rocks of Ohio and Indiana. 



mentioned above as containing abundant fossils. Since this lower 

 limestone occurs beneath the Ohio rock layer identified with the 

 Niagara shale of New York, it was natural to call it the Clinton forma- 

 tion. The identification was based, however, more upon stratigraphical 

 than paleontological grounds. Comparing the fossils described as 

 coming from the Clinton of New York with those undoubtedly found 

 in the so-called Clinton of Ohio, a number of identical species was 

 found. This is not at all surprising when it is remembered that the 

 Clinton formation in both states represents an earlier stage of develop- 

 ment than the Niagara and that in both states these faunae are found 

 just beneath the Niagara. The identity between the Clinton faunae 

 of the two states on closer examination is not found to be so close as 

 at first supposed. Whether this is due to geographical causes, the 

 Clinton of New York being more litoral, or whether it is due to 

 moderate differences of horizon, can not be told until the Clinton of 

 New York is much more closely studied. Although I have been 

 accustomed to call the Ohio formation the Clinton, yet I should be 

 willing to recognize the fact that the identity is not very marked, by 

 giving it a name of its own, for instance, the Montgomery formation y 

 on account of its typical development in Montgomery county, in Ohio. 



Below the Ohio Clinton was found along the eastern and northern 

 lines of outcrop, a layer of more argillaceous and sandy material, 

 forming in some parts of the state a quite firm stone. This is espec- 

 ially true along the more eastern line of outcrops, where the greater 

 abundance of lime in this stone gives it a firm texture. This forma- 

 tion is very rarely fossiliferous, if the presence of annelid teeth be 

 omitted. Since this formation, rarely exceeding 5 feet, occurs below 

 the limestone identified with the Clinton and has a sandy character, it 

 was identified at various times as the Medina. The presence of 

 Halysites catenulatus discovered at an eastern locality in Ohio recently 

 would seem to confirm this. The occurence of this one fossil is 

 however not determinative in face of the fact that when the formation 

 is traced westward it shows undoubted Lower Silurian fossils in the 

 corresponding formations there. It simply illustrates the fact observed 

 before, that, in many cases Upper Silurian fossils in Ohio seem to 

 have been introduced from the east. This is shown by the observa- 

 tion that certain fossils occur as low as the Clinton in more eastern 

 localities, in New York and Pennsylvania, but do not make their 

 appearance in the Clinton of Ohio, while they are found in the 



