Microscopical Study of ()/iio /.inies/oiics. i6'^ 



Ascendint^ tlie j^coloj^ical column of tlie vState, we next find 

 the 



CIJN ION CKOl'l', 



A narrow fringe forming the l)oundary between the lower 

 Silurian and Niagara foundations. The formation is of small 

 extent, and in composition is almost a pure carbonate of lime. 

 The limestone is highly fossiliferous, consisting of brachi- 

 opods, corals, and criuoids. 



This series in Ohio has been a disputed one, many contend- 

 ing it is only a part of the Niagara, but its invariably lighter 

 color, pure composition, and distinct fossils, many of which 

 are identical with the Clinton of other States, indicate a new 

 and distinct series. 



Thin sections show many fragments of Clathropora, probably 

 the clintoncnsis, a few fragments of Favosites, with other corals 

 and a few shells. One layer of a light brown color, probably 

 colored by iron, is quite compact, semi-crystalline, and only 

 sparingly fossiliferous. Another form of the rock is of a light 

 color, crystalline, and made up almost entirely of fragments of 

 crinoids, being a typical crinoidal limestone. The crystals 

 making up the remainder of the rock are calcite. Almost all 

 of the sections contain some fragments of crinoids, and this 

 was an age of crinoids, in distinction from the lower group. 

 On account of the beds of iron ore found at this horizon, and 

 the great yield of gas in the newer fields, it would be inferred 

 that vegetable life was abundant at this time, but there are no 

 definite proofs of the fact. The diversity of life continued 

 into this period, but many of the old forms have passed away 

 and new ones have taken their place. The limestone is more 

 compact, harder and more cystalline, almost a marble in 

 texture, and is a very pure carbonate of lime. The Clinton 

 period in Ohio w^as a brief one, and was followed by the more 

 extensive 



NIAGAR.V SERIES, 



Consisting of shales and a magnesian limestone, with consider- 

 able fossil life, which is mainly preserved in the form of 

 internal casts. The characteiistic forms being Pcmianicnis, 

 Trifucrel/a, MonoDierclla, and Atrypa. 

 The area extends over a large portion of vSouthwestern 



