FOSSIL FISHES. 603 



Europe. By these "finds" the fish-fauna of the two worlds has been 

 brought into closer agreement. 



That no actual or immediate communication existed between the 

 waters of Europe and of North America is rendered certain by the differ- 

 erence of the species. But that such communication had once existed 

 cannot be doubted when the obvious similarity of structure in the fossils- 

 indicative of genetic connection, is taken into account. 



Into this question however of Devonian and Silurian geography we 

 cannot here enter. The evidence is too indirect to admit of condensa- 

 tion into the space at our command. One point in connection with 

 these fossils is nevertheless of sufficient general interest to justify a short 

 notice. 



The line of descent of these strange armored monsters has not yet been 

 traced. They appeared suddenly in the waters of the Devonian seas and 

 at present stand as it were almost without father and without mother. 

 But no one accustomed to modern views of the relationship of the ani- 

 mal kingdom, fossil or recent, doubts that behind creatures of so com- 

 paratively high a development there must have existed ancestors nearly 

 as high, of which we at prtsent know nothing. The rocks below those 

 which have yielded such treasures must hold other treasures thus far 

 unknown — the fossils of earlier seas hitherto unfound. This statement, 

 will be better understood after examining the following table. 



The Cleveland Shale of Dr. Newberry (upper part of the Ohio Shale 

 of this report) is the stratum from which have been extracted nearly all 

 the fossils above alluded to. This is the uppermost part of the Devon- 

 ian of Ohio of most authors, but it was placed in the Carboniferous by 

 Dr. Newberry. Below it lie the beds as here given : 



a f Cleveland Shale Fish-fossils abundant. 



•2 Ohio Shale -j Erie Shale Fish- fossils absent. 



( Huron Shale Fish-fossils present. 



5 Hamilton Shale Msh-fossils absent. 



Corniferous Limestone Fish-fossils abundant, 



f Lower Helderberg Limestone. 

 I Salina Group. 

 Si'urian -] Niagara Limestone. 

 I Clinton Limestone. 

 [Medina Shale. 



Thus we see that while the Cleveland shale is so rich the immedi- 

 ately underlying Erie Shale is absolutely barren, but the still deeper and 

 therefore older Huron has yielded at least five species. Below this 

 again the Hamilton or Olentangy has, so far as I am aware, proved en- 

 tirely devoid of fish-remains, while the Corniferous Limestone, the base 

 of the Devonian rocks of the State, is even richer than the Huron, hold- 

 ing as it does several large and striking forms of ichthyic life and abund- 

 ant fragments of smaller species. It is hardly necessary to add that 

 the^e statements refer only to the State of Ohio. 



