2 Cincinnati Soc^ietyyof Natural History. 



sponds to the so-called Niagara shales of Adams and High- 

 land counties in Ohio. 



In former years, the name Beavertown marl was used for 

 a very fine grained limestone, 9 inches thick, weathering to a 

 rather soft rock, in which a small depauperate fauna, consist- 

 ing chiefly of a small species of Orthoceras and several gastero- 

 pods, was found. This rock occurred at Dayton, Ohio, in an 

 area about 4 or 5 miles in diameter, immediately above the soft, 

 richly fossiliferous clays with which the Brassfield bed termi- 

 nates in Montgomery, and adjacent counties, in Ohio. The 

 term marl, for the 9-inch layer, at the base of the Dayton lime- 

 stone, is not appropriate, and at present this layer is included in 

 the Dayton limestone. The richly fossiliferous clay at the top 

 of the so-called Clinton limestone of Ohio carries the same 

 fauna as the underlying limestone, merely more frequently as 

 free specimens, and, therefore, more interesting to the collector. 

 This clay never has received a separate designation, and in 

 my opinion does not need any. It is not the stratum to which 

 the name Beavertown marl was applied originally, but imme- 

 diately underlies the latter. 



In Lewis county, Kentucky, the Alger member of the Crab 

 Orchard formation is overlaid by a variable thickness of 

 Silurian limestone. This limestone was investigated by Mr. 

 W. S. Morse and myself at numerous localities, and a fair 

 fauna was collected, described on the following pages. This 

 limestone may be traced along the bold bluffs of the Ohio 

 river from the neighborhood of Vanceburg, in Kentucky, to 

 the mouth of Brush Creek, in Adams county, Ohio. Strati- 

 graphically it occupies the same position as the West Union 

 bed, in Adams county. No strata equivalent to the Spring- 

 field, Cedarville, or Hillsboro divisions of the Ohio Silurian 

 have been identified so far in Kentucky. 



In Lewis and Fleming counties, in Kentucky, the upper 

 part of the Crab Orchard formation contains more or less 

 thin-bedded indurated argillaceous shale. This phase con- 

 tinues northward into Ohio, and is well exposed west of 



