50 Cincinnati Society of Natural History. 



was deposited in shallower water when the land was nearer and the 

 land-wash more abundant. The shallowing and narrowing of the 

 Corniferous sea which produced this difference in the sediments 

 deposited in Central Ohio, was perhaps somewhat sudden, but the 

 change was not sufficiently great to destroy any considerable num- 

 ber of the mollusks which inhabited this ocean or to bring in any 

 new fauna. A little later the water became much shallower, and 

 was so loaded with sediment, that the marine life was wholly 

 changed. The corals and mollusks all disappeared, and the Huron 

 shale, deposited in this epoch, is remarkably barren of life. It 

 contains, however, the remains of great fishes peculiar to itself, 

 and what w r ere floating logs of Corniferous trees of large size. Rather 

 strangely these are about the only traces of land vegetation we find 

 in the Huron shale ; the carbonaceous matter, which composes one 

 tenth or more of the mass, having probably been derived from 

 Algas. Impressions of sea-weeds are found in great numbers on 

 some of the layers of the shale, but it h^s seemed to me that the 

 diffused carbon was probably in large part derived from minute if 

 not microscopic forms of aquatic vegetation. 



Caulopteris antioua. Xewb. 

 Plate IV. 



Stem three to four inches in diameter, marked with large, spirally 

 arranged and separated leaf scars ; scars about one and one-half 

 inches long by one inch wide, regularly arched above, the outline 

 marked by a raised rim. below horizontally truncated. The surface 

 of the leaf scars is somewhat irregularly pitted and striated. 



The only specimen of this plant known is a cast of a portion of a 

 trunk about eighteen inches in length by three and a half to four 

 inches wide. This bears on the exposed side twenty-two large 

 leaf scars, with the bases of some of the fronds still attached to 

 several of them. Between these scars the trunk is somewhat fur- 

 rowed. These scars are not perfectly defined in this specimen, as 

 the toot stalks of the fronds were apparently adherent to ail of 

 them when the specimen was fossilized. In the splitting of the 

 rock, those portions of the leaf stems which projected into the lime- 

 stone above the fossil were broken away, leaving an irregular frac- 

 ture at the base of each leaf scar, so that its lower outline, and that 

 portion of the surface which would naturally carry the vascular 

 .'mpressions, is concealed. The scars are distinctly separated from 



