"WITH THOSE OF NEW YORK. 275 



teristic fossils of the Trenton limestone, yet it may exist here, 

 and Mr. Vamixem informs me that he saw it in the valley of the 

 Little Miami, a locality which I did not visit.* 



Proceeding upward from the green shale with Triarfhnis, we 

 find a somewhat similar shale, with thin layers of sandstone, 

 characterized by the presence of Trinvcleiis and Graptolites. 

 Still above this we find alternations of shale, or marl, and lime- 

 stone, with Ortkis striatida in great abundance ; with this shell 

 and above it occur Strophomena sericea, S. alternata ? Pterinea 

 carinata, Cypricardia augnstifrons, C. modiolaris, CijrtoUtes orva- 

 tus, with a great abundance of corals and other fossils. Among 

 these are Bellerophon bilobatus, Orthocci'as, and two or more 

 species of OrtJtis similar to, or identical with, those of the Cara- 

 doc sandstone of England. Fragments of Isotelus are abundant, 

 also a species of Calijmene. 



From the enumeration of some of the forms, it will be per- 

 ceived that we have here an assemblage of fossils similar to that 

 of the Hudson river gi'oup of New York. For here, as in Ohio, 

 the shales, with Triarthrm, are succeeded by green shales and 

 slaty sandstones containing Trimicleus and Graptolites, vdxh 

 other fossils. The Orthis striatula, O. caUactis, Strophomena 

 nasuta, Pterinea and Cypricardia, are likewise characteristics of 

 this gi'oup, as well as Bellerophon bilobatus and the same spe- 

 cies of Orthoceras. Strophomena sericea occurs in Ohio, com- 

 pletely covering the surface of thin layers of limestone, as in 

 New York. In both places are seen thin courses, composed 

 almost wholly of the stems of Crinoidea, and the species appear 

 to be identical. 



The remains of Isotelus, several species of which occur, have 

 always been considered sufficient proof of the identity of this 

 rock with the Trenton limestone of New York, and these fossils 



* Very careful and extensive examination is often necessary, in order to identify rocks 

 by the presence of characteristic fossils. In the rocks of Cincinnati, Maysville, and 

 other places, occur fossils of the Trenton limestone. T^jnong them are Ortkis str/ntii/a, 

 StropJiotnena {Leptana) sericea, S. alternata? Belleropkon bilobatus, Favosites lycopcr- 

 don, and others. The last named fossil occurs with Bellerophon bilobatus and Orthis 

 striatida in the Caradoc sandstone of England. The Calymene of these rocks at the West, 

 usually considered identical with the Trenton species, is probably distinct. 



