58 O RISK ANY GROUP. 



CHAPTER XIX. 



ORISKANY OROUP. 



119. This Group was defined as the Oriskany sandstoue by Vanuxem, in 

 1839, and named from the white sandstone occurring at the Falls of the Oriskany, 

 in Oneida County, N. Y., where it is about 20 feet in thickness. It forms a narrow 

 belt of rough sandstone from the Hudson to Cayuga Lake, charged with peculiar 

 fossils, and varying from a few inches to 30 feet in thickness. It stretches south 

 in the Appalachian region through Pennsylvania, Maryland, and Virginia, and has 

 a thickness in Pennsylvania of 300 feet. It appears in New Jersey with a thick- 

 ness of 130 feet. In Maine there is a large exposure between Parlin Pond and 

 Aroostook, and it exists at Gaspe and in Nova Scotia. It is known in Canada at 

 but few places, one of the principal exposures being at North Cayuga, and cover- 

 ing only 230 acres. In Southern Illinois it is underlaid with silicious limestone, 

 called the Clear Creek limestone, which constitutes incomplete passage-beds from 

 the Upper Silurian. It is also known in Missouri. 



120. It appears as a belt deposited upon the shores of the islands which then 

 existed, and to mark their outlines in a greater or less degree. Like other arena- 

 ceous deposits, it indicates the presence of land and shallow water. It abounds in 

 the casts of Brachiopods and Gasteropods in New York, Maryland, and Virginia, 

 and in some places Crinoids occur. The characteristic species are Spirifera arenosa, 

 S. arrecta, S. pyxidata, Rensselaeria ovoides, Orthis proximw, 0. musculosa, Strophodoiila 

 magniventra, S. magnified, Gyrtina rostrata, Eatonia peeuliaris, Leptocceliaflabellites, and 

 Plaiystoma ventricosum. In some places in Virginia the shells are silicified and quite 

 free from adhering matter, and the exterior markings and iuternal structure are well 

 preserved, even the internal coils of Brachiopoda are beautifully represented. Near 

 Cumberland, Md., a few elegant crinoids have been found, and one Cystideau, 

 An0malocy8tite& disparttw, which is the latest known representative of that order, ex- 

 cept Strobilocyatites calvini. 



121. The Brachiopods are Devonian in their character rather than Silurian, 

 and there is graduation to the succeeding rocks through the Cauda galli grit, which 

 is a dark, gritty slate, bearing few fossils. The rocks are not such as to have pre- 

 served land-plants very well ; but they should have preserved fish-teeth if any then 

 existed, but no trace of them has been discovered. 



