Geological Society of France for 1847. 161 



gives an account of the groups, thirty-eight in number, into which 

 the palaeozoic rocks of Ohio, Kentucky, and Indiana, have been di- 

 vided, and then proceeds to examine into the paialleHsm of these 

 North American deposits with the older fossiliferous rocks of Eui'ope. 

 He investigates this subject upon the principle, that if in two coun- 

 tries a certain number of systems, characterised by the same fossils, 

 are superimposed in the same order, whatever may be the thickness 

 or number of the physical groups of which they are composed, these 

 systems should be considered as parallel and synchronous. 



The American series is so complete, its parts being conformable 

 and passing into each other, that marked divisions cannot be esta- 

 blished. Hence it follows that the limits corresponding with the 

 different European systems are in some cases uncertain, but this is 

 considered as of less consequence if the middle parts of each system 

 can be established. The important point, M. de Verneuil adds, is to 

 feel assured that during the palaeozoic period the animal kingdom 

 upon the area occupied by the two continents has suffered simulta- 

 neous transformations, so that identical species occupy the same geo- 

 logical positions. 



The six lowest New York groups, from the Potsdam sandstone to 

 the Hudson River group inclusive, are referred to the Lower Silurian 

 rocks, the lingula sandstone of Potsdam being probably equivalent to 

 the obelus sandstone of Russia and the lower sandstones of Scandi- 

 navia. The siliceous limestone, with the Black River and Trenton 

 groups, are referred to the bituminous slates and the orthoceratite 

 limestones of Sweden and Russia, while the Utica slates and the Hud- 

 son River groups, with the Graptolites at their base, are considered 

 equivalent to the graptolite slates of Sweden, succeeding the red 

 orthoceratite limestone, and also to those of Bain in France. Trilo- 

 bites were largely developed both in Europe and America at this pe- 

 riod, and the genus Isotelus represents in the latter the Asaphus of 

 the former. Orthoceratites were abundant, and Bellerophon appeared 

 in connection with this early life, marked also by the presence of 

 Orthis, LeptcEua, and Terebratula. 



The New York groups, rising above those mentioned, up to the 

 Oriskany sandstone exclusive, are referred to the Upper Silurian 

 rocks, the Niagara limestone and shales being considered equivalent 

 to those of Wenlock and Gothland. Trilobites were still abundant, 

 some species being rare and limited to thin groups of rocks, such as 

 Phacops Hausmanni, Sphcerexochus minus, and Cheirurus insignis- 

 Orthoceratites are less abundant than in the lower series. Spii'ifers 

 and Tentaculites appear, and large corals are found, such as Favosites 

 Gothlandica, &c., while Graptolites cease. Of forty identical species 

 found in the Upper Silurian rocks of America and Europe, M. de 

 Verneuil considers that thirty-two have neither lived before nor after 

 this period. 



The New York groups, from the Oriskany sandstones to the sand- 



VOL. XLV, NO. LXXXIX. — JULY 1848. L 



