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 in. It is evident, whether these 

 terms describe this formation "high 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, r.3, c. 6 feet, ] 



Non-fossiliferous bed, F.3, b, 5 feet, } St. Peter Shell limestone. 



Lower Shell limestone, F.3, a, 23 feet, j 



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 Iowa, 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. b. 



=Utica slate and Hudson Eiver 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 3 b. Lead-bearing beds of the Upper Magnesian limestone. 



2. Formation 3 a. 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: 



