i66 Citiciiina/i Society of Natural History. 



DEVONIAN, 



or Corniferous, extending, as a narrow strip, 8-20 miles in 

 width, through central portion of the State. The limestone 

 is quite a pure carbonate, abundantly fossiliferous, containing 

 brachiopods and reef building corals in great abundance. It 

 is here that we find the first abundant plant and fish life pre- 

 served. 



At Columbus, probabh-, the best development is to be found. 

 The upper portion is shaly, with very few fossils, and these 

 are mainly fish remains ; below this stratum comes a brown 

 and white chert, which is not acted upon by acids. The fos- 

 sils in this chert are very finely preserved, even the delicate 

 markings coming distinctly to view. Below this comes the 

 bone bed, a comparatively thin layer made up of the teeth 

 and remains of fish, while below this lies the great mass of 

 limestone used for lime and building purposes. The micro- 

 scope reveals many interesting and puzzling fossil forms. 



The brown chert is very compact, but contains a few frag- 

 ments of shells, crinoid joints, and a number of light spaces, 

 highly crystalline, whose origin is to be traced to the replace- 

 ment of organic life by crystalline matter. 



The white chert is more abundantly fossiliferous. even to the 

 naked eye, but under the microscope it is one mass of fossil 

 life, crinoid stems being especially numerous. There are a 

 number of forms belonging to the group Porifcra, or the order 

 of sponges, sponge spicules being found through the rock. 

 This is the first time they have been reported from the Ohio 

 Devonian. The chert has an organic origin, and we have a 

 good example of a silica replacement of limestone. We can 

 even make a series of gradations to this end; starting with the 

 limestone, then raking the white chert, abundantly fo.ssilifer- 

 ous in many places, then the brown chert, which is only 

 slightly fossiliferous, and I have found several specimens of a 

 hard brown chert covered by a layer of perfect minute quartz 

 crystals, and this again covered by chert, suggesting a still 

 further change, due to partial solution and deposit. This 

 accords very closely with the observations with regard to the 

 carboniferous flints made by Dr. Hinde, of England, 

 whereby he proves their organic origin. 



The limestone proper is mainly compact and semi-crystalline, 



