Ch. xxvl] in the united states. 427 



same conclusion.^* The resemblance of the Spirifers of tliis Oriskany 

 sandstone to those of the Lower Devonian of the Eifel was the chief mo- 

 tive assigned by M. de Yerneuil for his view ; and the overlying Schoharie 

 grit, No. 10, was classed as Devonian because it contained a species of 

 Asterolepis. On the other hand. Prof Hall adduces many, fossils from 

 Nos. 10 and 12 which resemble more nearly the Ludlow group of Mur- 

 chison than any other European type ; and he thinks, therefore, that those 

 groups may be " Upper Silurian." Although the Oriskany sandstone is 

 no more than 30 feet thick in New York, it is sometimes 300 feet thick in 

 Pennsylvania and Virginia, where, together with other primary or paleo- 

 zoic strata, it has been well studied by Professors W. B. and H. D. Rogers. 

 The upper divisions (from the Catskill to the Genesee groups, inclu- 

 sive, Nos. 1 to 4) consist of arenaceous and shaly beds, and may have 

 been of littoral origin. They vary greatly in thickness, and few of them 

 can be traced into the " far w^est ;" whereas the calcareous groups, Nos. 

 8 and 9, although in New York they have seldom a united thickness of 

 more than 50 feet, are observed to constitute an almost continuous coral- 

 reef over an area of not less than 500,000 square miles, from the State of 

 New York to the Mississippi, and between Lakes Huron and Michigan, in 

 the north, and the Ohio River and Tennessee in the south. In the 

 Western States they are represented by the upper part of what is termed 

 " the Cliff Limestone." There is a grand display of this calcareous for- 

 mation at the falls or rapids of the Ohio River at Louisville in Kentucky, 

 where it much resembles a modern coral-reef. A wide extent of surface 

 is exposed in a series of horizontal ledges, at all seasons when the water 

 is not high ; and, the softer parts of the stone having decomposed and 

 wasted away, the harder calcareous corals stand out in relief, their erect 

 stems sending out branches precisely as when they were living. Among 

 other species I observed large masses, not less than 5 feet in diameter, of 

 Favosites gotldandica^ with its beautiful honeycomb structure well dis- 

 played, and, by the side of it, the Favistella, combining a similar honey- 

 combed form with the star of the Astrcea. There was also the cup- 

 shaped Cyathophyllum^ and the delicate network of the Fenestella., and 

 that elegant and well-known European species of fossil, called " the chain 

 coral," Catenipora escharoides (see fig. 579, p. 435), with a profusion of 

 others. These coralline forms were mingled with the joints, stems, and 

 occasionally the heads of lily encrinites. Although hundreds of fine 

 specimens have been detached from these rocks to enrich the museums 

 of Europe and America, another crop is constantly working its way out, 

 under the action of the stream, and of the sun and rain in the warm sea- 

 son when the channel is laid dry. The waters of the Ohio, when I visited 

 the spot in April, 1846, were more than 40 feet below their highest level, 

 and 20 feet above their lowest, so that large spaces of bare rock were ex- 

 posed to view.f 



* De Yerneuil, Bulletin, 4, 618, 184Y. D. Sliarpe, Quart. Journ. Geol. Soc. vol 

 iv. pp. 145, 1847. 



f Lyell's t^econd Yisit to the United States, vol li. p. 277. 



