xl 



THE PALEONTOLOGY OF MINNESOTA. 



Closes Sfrony. 



IMS. Iii volume n of the final report of the late Wisconsin survey is a chapter by 

 MOSES STRONG on the " Geology and Topography of the Lead Region." Under the term 

 Trenton he embraces the Buff and Blue limestones, their total average thickness being 

 about 50 feet. The Blue is divisible into two parts, viz., the "glass rock," in heavy lay- 

 ers, the lower half, and the other thin-bedded which sometimes graduates into the thin- 

 bedded Galena above. At the separation of the Blue from the Galena, occurs almost invar- 

 iably, a carbonaceous shale, having a thickness from a quarter of an inch to a foot or more. 

 This is considered an unfailing guide to the bottom of the Galena. This shale has its 

 greatest thickness in the vicinity of Shullsburg, where it is seven feet thick. the carbonace- 

 ous matter amounting to 43. 60 p. c. Large quantities of lead, and more particularly of zinc, 

 have been taken from the Blue and Buff limestones in southwestern Wisconsin. 



The Galena limestone is a dolomyte and is the chief lead-bearing rock. It is regularly 

 bedded and has a thickness of 200 feet or more. It is apt to weather with an irregular 

 surface owing to cavities and softer spots. Its lower portion is interbedded with thin lay- 

 ers and irregular nodules of flint. The characteristic fossil of the formation is Recep- 

 taculites oweni, found indifferently in all parts. Next in frequency are Streptelasma cor- 

 niculum and some species of Orthis. The most infrequent is Maclurea magna. which per- 

 tains to the middle beds. Lingula quadrata is quite frequent in the upper beds. Other 

 and more infrequent fossils are Pleurotomaria lenticularis, Bellerophon bilobatus. Orthis 

 biforata and occasional Orthocerata. 



The Cincinnati, which rarely contains important layers of limestone, has a thickness 

 of about 125 feet. The lower beds abound with shells of the Nucula fecunda. and the 

 middle ones with Rhynchonella increbescens.Strophomena alternata and stems of Chanetos. 

 The upper beds contain a few Orthocerata. 



R. P. Whitfield. 



1879. Description of new species of fossils from the Paleozoic formations of Wisconsin, by 

 R. P. Whitfield; Ann.Rept. Wisconsin Geol. Survey for 1879; Madison. 1880; pp. 44-71. 



Twenty six new species are described in this paper. The Trenton forms. ten in 

 number, are as follows: 



ZVocAonema beachi, Buff beds of lower Trenton. 



Endtxxras (Cameroetras) subanntilatttm, upper part of ButT limestone. 



Cyrtoceras planidomitum, lower part of Buff limestones. 



Oncootrof inumiaforme, Lower Buff limestone. 



Oncoceras brericurvatum, upper part of Buff limestones. 



!'liugtria>igulatn$. Blue limestone. 

 Fittulipora ruyosa, Hudson River shales. 



'orhynch it* CM nlinult, Hudson River shales. 

 x :>phomcna tcisconnincnsis, Hudson River shales. 

 Rhyitchonelltt neenah, Trenton, Galena and Hudson River. 



Those forms are illustrated in volume iv of the final report. 



