HISTORICAL SKETCH. XXV 
Dr. Owen, in the preparation of his report (pp. 71-73), evidently included in form- 
ation 3 not only the Trenton, as seen at the falls of St. Anthony, but also rocks of the 
horizons of the Hudson River, the Galena and the Niagara limestones, thus not recogniz- 
ing the Upper Silurian. This is apparent from the following remarks, p. 73: 
“Many species found both by Dr. Shumard and myself, in the lower shell limestone of the Upper 
Mississippi are identical with forms occurring both in the substratum of gray limestone at Eagle Point 
in the Dubuque district—figured and described in my report of 1839—and in the blue limestone of the 
Ohio valley. Those of the upper division [For. 3, c], resemble rather the species found in the inferior 
beds of the Upper Magnesian limestone of that district. But all, so far as our examinations have yet 
extended, are of Lower Silurian type.” 
There is, therefore, some contradiction between the earlier and later portions of this 
magnificent report, and in the application of the characters (F. 3, a, band c), by which he 
chose to designate the different parts of Formation 11. It is evident, whether these 
terms describe this formation ‘thigh up on the Turkey river” (p. 73), or ‘‘on the heights 
at Fort Snelling,” that the lettering of the parts, and the descriptions of the sections (see 
Sec. 2, R. at the falls of St. Anthony) are intended to be applicable to the same beds, 
although the thickness is supposed to be greatly reduced at the falls of St. Anthony. 
The general report passes from this immediately to the Devonian as it occurs on the 
Cedar and Lower Iowa rivers, in Iowa. At the falls of St. Anthony, however, Dr. 
Shumard’s section, to which Dr. Owen refers, is as follows (Plate, Sec. 2, R.): 
Upper Shell limestone, F.3, ¢.6 feet, | 
Non-fossiliferous bed, F.3, 6, 5 feet, | St. Peter Shell limestone. 
Lower Shell limestone, F.3, a, 23 feet, | 
In the final discussion of the paleontological results as presented in the tables at the 
end of the volume, it becomes apparent that Dr. Owen had discovered that under the 
designation ‘‘ Formation III,” especially in lowa, he had included some beds which actually 
contained an Upper Silurian fauna, and the following section is finally given, [see table, 
p. 624. | 
Coralline and Upper Pentamerus beds, F. 3. c. Upper Silurian. _ 
=Clinton and Niagara group of New York. 
Lead-bearing beds of the Upper Magnesian limestone, F. 3. 0. 
—Utica slate and Hudson River group of New York. Lower Silurian. 
Shell beds, F. 3, a—Trenton limestone of New York. Lower Silurian. 
The term ‘‘St. Peter’s Shell limestone” therefore is here made the equivalent not only 
of the shell beds described by Shumard at the mouth of the St. Peter’s (Minnesota) river, 
but of all the Trenton beds, or ‘‘ Blue limestone,” up to the base of the lead-bearing beds, 
_ which at St. Paul carries the St. Peter shell limestone to near the summit of the hills, or 
about 90 feet higher than proposed by Shumard. 
The strata covered by the scope of the present volume are arranged by Owen in the 
following scheme: 
1. Formation 3b. Lead-bearing beds of the Upper Magnesian limestone. 
2. Formation 3a. St. Peter’s shell limestone. 
The second of these was divided into three parts by Dr. B. F. Shumard under the 
following distinctions as seen at St. Paul and the falls of St. Anthony, in descending 
order: 
