XC THE PALEONTOLOGY OF MINNESOTA. 



The St. Peter sandstone has a wide geographical distribution, being known by 

 outcroppings in Canada, Michigan, Wisconsin, Minnesota, Iowa, Illinois and Missouri, 

 and through deep borings in Indiana, Ohio and Kentucky. In the northwest it consists 

 almost entirely of silica, but in the vicinity of Cincinnati, where it is the principal source 

 of the " blue lick water " of the artesian wells, it contains a considerable amount of 

 calcareous material. 



Stones River group. 



This name was proposed by Prof. J. M. Safford in 1851 (Amer. Jour. Sci. and Arts, 

 2d ser., vol. XII, p. 352) for the Lower Silurian strata of central Tennessee which in his 

 "Geology of Tennessee," 1869, we find fully described under the names Central limestone, 

 Pierce limestone, Ridley limestone, Glade limestone and Carter's Creek limestone. In the 

 latter publication the group name is abandoned under the misapprehension that the 

 limestones so designated are strictly equivalent to the Trenton group of New York. As 

 we are confident that this was an error, we propose to resurrect the name. In our 

 opinion the four lower members of the Stones River group as originally defined, are 

 equivalent to the Birdseye limestone of New York and the " Lower Buff " and "Lower 

 Blue " limestones of the Trenton, in Illinois, Wisconsin, Iowa and Minnesota. The group is 

 strongly developed in Kentucky and from here it doubtless extends as an unbroken, though 

 diminishing sheet, westward into Missouri and northward into Canada. According to the 

 evidence now available it seems that in geographical distribution, thickness, and paleon- 

 tological interest, the Stones River group is nearly or quite equal to the Trenton limestone 

 itself. 



Being thin and, according to report, not readily distinguished paleontologically from 

 the overlying Black River limestone in Canada and New York, the Birdseye limestone, 

 a name that we think must give way to the geographic designation proposed by Prof. 

 Safford, has not been generally recognized. In Tennessee and the western and north- 

 western states the group has been almost universally regarded as representing part if not 

 all of the Trenton limestone, while the Galena limestone, which is the exact equivalent of 

 the Trenton limestone, was by most investigators believed to represent a local upper 

 member of the Trenton, and by others the western equivalent of the Utica slate. 



A careful and extended investigation of the stratigraphy and paleontology of the 

 Trenton and Cincinnati periods, however, proves most conclusively that the generally 

 accepted views of the equivalents of the Galena and other limestones resting on the St. 

 Peter sandstone are incorrect, and that Prof. James Hall's early surmise respecting the 

 presence in the northwest of strata representing the Birdseye and Black River limestones 

 of New York is essentially correct. 



As regards the Nashville group, which Prof. Safford, chiefly because of the presence 

 of two fossils, Cyrtolites ornatus and Byssonychia (Ambonychia) radiata, in 1869, concluded 



