CONTRIBUIIONS TO PALiEONTOLOGT. 119 



10. PRELIimARY NOTICE OF THE FAUNA OF THE POTSDAM 



SANDSTONE; 



WITH EEMaRKS UPON THE PEETIOUSLY KNOWN SPECIES OF FOSSILS, AND DESCRIPTIONS 

 OF SOME NEW ONES, FBOM THE SANDSTONE OF THE UPPER MISSISSIPPI VALLEY.* 



In the final nomenclature of the New- York geologists, the name 

 Potsdam sandstone was adopted for the lowest stratified rock of 

 the series known to contain fossils. The fossils of this rock then 

 known, however, were so few, and their character such as to afi'ord 

 very unsatisfactory means of comparison with the fauna of any 

 distant formation. It was nevertheless considered by them to hold 

 a lower position than any of the rocks then recognized as con- 

 stituting the Silurian System of Great Britain. Up to the time of 

 publishing the first volume of the Palaeontology of New-York in 

 1847, little had been added to the fossils before known from the 

 New-York localities. In fact, neither time nor means for its ex- 

 ploration had been placed at the disposal of the author of that 

 work, and the necessity of making collections and publishing 

 within a limited time prevented such investigations as would have 

 been desirable. Since that period, little has been added to the 

 species before known from New- York localities, except a single 

 species of Conocephalites discovered by Mr. Bradley at Keese- 

 ville. 



At a later period (1847 - 50), Dr. D. D. Owen, in his investiga- 

 tions in Wisconsin, Iowa and Minnesota, discovered, in the sand- 

 stone of the Upper Mississippi valley, a comparatively abundant 

 fauna, which he at first regarded as marking a horizon far below 

 the Potsdam sandstone of New- York, having considered the St. 

 Peters sandstone as the equivalent of that rock. In pursuing some 

 investigations in connection with the United States Survey of the 

 Lake Superior region in 1850, I had an opportunity of tracing the 



* A notice of this paper was read before the Albany Institute, April 29, 1862; and 

 by an arrangement between the Publishing Committee and the Regents of the Uni- 

 versity, it appears in this connexion. 



The receipt of Dr. Shumard's paperf in June 1862, has enabled the writer to add 

 some farther information regarding the species described by Dr. D. D. Owen from^the 

 same formation. 



t " Notice of some new and imperfectly known Fossils from the Primordial zone 

 Potsdam sandstone and Calciferous Sand group) of Wisconsin and Missouri,'' by 

 . F. Shumard. Transactions of the Academy of Sciences, St.Louis, May 1862. 



