December, 1843.] 329 



proportion of oysters to the other bivalves is about the same which the dredge 

 furnished at the mouth of Cape Fear river, N. C. at the depth of 8 fathoms. 



"With the many interesting bivalves of Petersburg I found a valve of the 

 beautiful 



Pholadomya abrupta. 



which Deshayes has referred to Panopoea. I carefully removed the marl from 

 the hinge, in order to ascertain if there was an erect curved tooth as in Pan- 

 opcea, but the hinge proved to be destitute of any kind of tooth or process, and 

 closely resembles that of the recent Pholadomya. Two characters, therefore, 

 remove this shell from the genus Panopcea,- the pearliness of the substance and 

 the absence of a cardinal tooth. A true panopoea is never pearly, any more 

 than a Unio is ever otherwise. 



Observations on the Lead Bearing Limestone of Wisconsin, and descriptions 

 of a new genus of Trilobites and fifteen new Silurian fossils. 



By T. A. Conrad. 



As the galeniferous limestone of Wisconsin and Galena has attracted the 

 attention of our most distinguished Geologists, who have endeavored to assign 

 its relative position in the scale of formations, I hope it may not be deemed pre- 

 sumptuous if I endeavor to assist in settling a question of so much importance. 

 The difficulty has hitherto arisen from the scarcity and obscurity of characteris- 

 tic fossils, which is now in a great measure removed. Some years since I had 

 the pleasure of examining a series of organic remains collected by Richard C. 

 Taylor, Esq. at the lead mines in Wisconsin, and then distinctly recognized the 

 species which belong to the Trenton limestone of New York, a rock which, in 

 my first report on the Geology of New York, I showed to be an independant 

 formation, and entirely distinct from any above or below it. Since then I have 

 proved its occurrence at Cincinnati, in Ohio, and at Carlisle and Bedford 

 Springs, Pennsylvania. In these remote localities the fossils are generally the 

 same species, and the group of a unity which admits not of doubt or ambiguity. 



The specimens found by Mr. R. C.Taylor are chiefly from the limestone below 

 the lead, and consist of Bellerofhron bilobatus, (Sowerby.) 



There are also specimens of fossiliferous limestone from Cassville, Wisconsin, 

 of the same age, containing a Trenton limestone species of Orthis, like C. callac- 

 tis, a Naculite, occurring also near Middleville, N. Y., Belleuofhron bilo. 

 batus, a Strophomena like Orthis alternata, Sowerby, a common shell in the 

 New York Trenton limestone, and an Orthis resembling O. tcstudinaria, still 

 more abundant in the same rock. 



In the same collection are carboniferous fossils, in limestone and in chert, from 

 St. Genevieve, Missouri. The species consist of a large Bellerophron, 

 three species of Productus and one of Atrypa, all of which are found only in 

 the carboniferous or mountain limestone. 



I am indebted to the liberality of Mr. Stephen Taylor, who has recently re- 

 turned to this city from Mineral Point, Wisconsin Territory, for an opportunity 



