8 BULLETIN OF THE LABORATORIES 



a few inches to several feet in thickness, and corresponding in position 

 to with those of Fair Haven and Todd's Fork, in Ohio — the so-called 

 Medina. 



The top of the Upper Silurian of Indiana has also been well de- 

 termined. It consists ol the highly magnesian rock known as the 

 Guelph, in Canada, and the Cedarville, in Ohio. It has been identi- 

 fied in Grant. Madison, Delaware, and Randolph counties ( 13th Rep. 

 Ind. Geol. Surv); across the line it occurs again in the north of Preble 

 county, Ohio. 



In Ohio the Springfield beds have been identified at Eaton, Preble 

 county ; and the West Union beds seem to be entirely lacking. The 

 Springfield strata are in reality very closely allied to the Cedarville 

 strata, and are distinguished mnnly by the great abundance of the 

 brachiopod, Petamerus ohlon^us, and by the fact that it usually shows a 

 more decided tinge of blue. The blue magnesian rocks imrnediately 

 to the south of the Ciuelph series already mentioned may safely be re- 

 ferred here. 



In Ohio the E.iton beds extend south, reaching to a distance with- 

 in four miles of the Clinton exposures at Fair Haven. About two 

 miles north of the latter, the intervening portion is seen to contain 

 limestone beds, and also some cherty layers, one of which is well 

 marked, about nine inches thick, and contains numerous specimens of 

 Atrypa reticularis. Now // the cherty layers here may be considered 

 fairly equivalent with the cherty beds usually found beneath the 

 Waldron fossil beds of Indiana, then the Waldron beds may fairly 

 be considered the equivalent of the Upper Niagara shales of 

 Ohio and perhaps to contain sufficient association with the 

 Springfield beds to give its fauna a tinge of the facies of the Guelph. 

 The part below the cherty l)ed> in Indiana would then contain the 

 materials recognized in 0!iio as Clinton, Dayton, and perhaps the 

 lower part of the Niagara shale strata. The Clinton has been report- 

 ed from various parts of Indiana, but until the paleontological proofs 

 for such references are given, it will be impossible to make any use of 

 the identifications so far made. 



Paleontological facts also bear out these conclusions. The fauna 

 of the Waldron shales has ([uite a decided relation to the Guelph fos- 

 sils. It is not a typical Guelph fauna, but it has a facies approaching 

 that of the Guelph and a fair number of species are identical. The 



