xe THE PALEONTOLOGY OF MINNESOTA. 
The St. Peter sandstone has a wide geographical distribution, being known by 
outcroppings in Canada, Michigan, Wisconsin, Minnesota, Iowa, Llinois 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, 
aname 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 
