330 [December, 1843. 



to investigate some organic remains of more than ordinary interest, which that 

 gentleman procured at the lead mines. Accompanying these are specimens of 

 fossiliferous limestone, shells, and fragments of Trilobites in beautiful relief 

 upon the surface, and so familiar and characteristic, that at the first glance I 

 recognized the Trenton limestone of New York. The most prominent of these 

 fossils consist of the trilobites, Ceratjrcs pleurexanthemus,Is<yvEivs gigas, and 



Ill23nus , and of the shells, Strophomen a sericea, Phragmoljtes 



compressus, and Bellerophron bilobatus. With these are a large Cytherina, 

 known also to occur in the Trenton limestone of New York: the Terebra- 

 tula (Atrypa) Schlottheimii of Von Buch, and some beautiful new species of 

 bivalves. The limestone is very compact, replete with shells and favosites, of 

 a light color, inclining to drab, and it immediately underlies the rock in which 

 the galena occurs, as Mr. Taylor informs me. Many of the fossils are loose 

 and exceedingly well preserved, having apparently come from a soft limestone 

 shale. 



In examining, a few years since, some specimens of limestone brought from 

 Galena, by the late lamented Nicollet, and which he informed me, was ihe rock 

 immediately below the lead-bearing strata, I recognized the group of fossils 

 which characterize the Trenton limestone, but Mr. Nicollet was unable to pro- 

 cure any organic remains from the overlying rock, which might furnish a clue 

 to its geological age. Mr. Taylor has fortunately obtained this desirable object, 

 in Wisconsin, having discovered not only well preserved fossils, in the lead-bear- 

 ing formation, but even shells and remains of crinoidea replaced by the 

 sulphuret of lead. There is particularly the cast of a large Turritella com- 

 posed entirely of this mineral, and a specimen of Pleurotomaria anguluta, 

 which is a limestone cast, with the upper part of the spire of galena, and from 

 fragments yet remaining between the caste and matrix, it is evident that the 

 shell itself had been replaced by the sulphuret of lead. These two shells are 

 not uncommon in the Trenton limestone of Lewis county, New York. The 

 Turritella I have never known to occur in any other formation but the Phuro- 

 tomaria I found also in the Salmon river, or Pulaski shale, near Rome, Oneida 

 county. Mr. Taylor has likewise a crinoidal column, almost wholly replaced 

 by galena: it has distant very prominent rings or ridges, and is a species which 

 has been observed in the Trenton limestone of New York. 



From the evidence it is clear that the limestone of Galena, Illinois, and of 

 Mineral Point, Wisconsin, in which the lead occurs, is certainly not of more 

 recent date than the Pulaski and Lorraine shales of New York, and the cara- 

 doc sandstone of Great Britain : but I believe it will prove to be an upper mem- 

 ber of the Trenton limestone formation. 



Mr. Taylor has also a specimen of Trenton limestone, precisely similar to 

 that of Galena and Mineral Point, which was found in Wisconsin, 40 miles 

 N. E. of Galena. 



There is a specimen of the sulphuret of lead, among the cubes of which is 

 imbedded a single valve of Strophomena, very thin and silicified. 



Mr. Taylor brought the Pentamerus oblongus, Catexipora escharoides, 

 and C. labyrinthica, which were found together on one of the hillocks or 

 mounds," as they are termed in Wisconsin. These two fossils, when associ- 



