ERIE COUNTY. 191 



as the " Sandusky stone," and largely used for building, paving, and flag- 

 ging at Sandusky and elsewhere. The lower portion is light-colored, 

 and much more massive, and is that quarried at Kelly's Island and 

 Marblehead. The fossils of the Corniferous limestone are exceedingly 

 numerous and of great interest. Like most other limestones, this has 

 been derived from the decomposition of organic structures, and in many 

 places it is almost altogether made up of corals and shells. In chemical 

 composition it is a magnesian limestone, containing twenty per cent, or 

 more of magnesia. This peculiarity has been quoted as objectionable in 

 its adaptation to the manufacture of lime; but, on the contrary, it is 

 benefited by this ingredient, the magnesia making it slower in setting, 

 "less hot," as the masons say, and therefore much more manageable. 



The Corniferous limestone has been so fully described in the first vol- 

 ume of our report, both as regards its physical characters and fossils, 

 that little need be here said of its general relations. It is proper, how- 

 ever, that I should here refer to the views advanced by Prof. Winchell 

 in the reports on Delaware and Paulding counties, and which are not 

 quite in accordance with those I have expressed in regard to the age of the 

 upper, or Sandusky, member of the Corniferous limestone. It is claimed 

 by Prof. Winchell that because it contains certain mollusks that are usu- 

 ally called Hamilton fossils, such as Cyrtia Hamiltonensis, Spirifera mucro- 

 nata, and Athyris spiriferoides, it must necessarily be Hamilton ; but with 

 the exception of Spirifera mucronata, which I have never found in the for- 

 mation except at its very summit, all the other Hamilton fossils found in 

 the Sandusky limestone are such as are also found in the Corniferous of 

 New York, and therefore they constitute no reliable evidence of the 

 Hamilton age of the deposit. On the contrary, the Sandusky limestone 

 contains quite a large number of fossils which are not only common in 

 the lower, or Kelly's Island, subdivision of the Corniferous, but are re- 

 garded as. characteristic fossils of the Corniferous in New York, and are 

 not found in the Hamilton. We also have in the Sandusky limestone 

 all the remarkable fossil fishes — alluded to further on, and more fully de- 

 scribed in our palseontological reports — which form the most striking 

 features of the fauna of the Lower Corniferous (Kelly's Island and Co- 

 lumbus) limestone. None of these have ever been met with in the 

 Hamilton of New York; The. Corniferous mollusks alluded to above as 

 found in the Sandusky limestone are Spirifera acuminata, S. gregaria, S. 

 macra, Pentamerus aratus, Strophodonta hemispherica, Tentaculites scalaris, 

 etc. Of these, only the first has ever been found in the Hamilton, and 

 this, perhaps, but in a single instance in New York, while it is locally 

 nearly as abundant in the Sandusky as in the Kelley's Island limestone. 



