236 C. P. BERKEY PALEOGEOGRAPHY OF SAINT PETER TIME 



Ulrich and Winchell* correlate the 300 to 400 feet of Stones Kiver 

 limestones and shales of Kentucky and Tennessee with the 23 feet of 

 limestone just above the Saint Peter in Minnesota, remarking that the 

 Minnesota organic forms are most like those of the uppermost member 

 of the Stones Elver of Kentucky. 



Part of the Knox dolomite of Tennessee below the Stones Eiver group 

 is also credited to the Ordovicic ; how much should be is not known ; but 

 this much is clear, that in the Kentucky-Tennessee area there was con- 

 tinuous marine deposition, chiefly of a limestone character, amounting 

 to probably 1,000 or 1,500 feet, during the time from the close of the 

 Cambric to the end of Stones Eiver time — a period marked in the north- 

 west by the deposition of 75 to 150 feet of shaly limestones and dolo- 

 mites and 150 feet of sandstone, within which there is at least one break 

 of some significance. 



Only the upper representatives of the Stones Eiver group also are to 

 be seen in western New York, where the Lowville overlaps against the 

 earlier formations, as noted by Ulrich. 



Broadheadf calls attention to the interpolation of 80 to 190 feet of 

 the Missouri survey's "First Magnesian" between the Saint Peter and the 

 "Trenton limestone." This formation does not appear at all in the 

 northernmost areas, and, while the underlying magnesian formation has 

 a thickness in Missouri of 150 to 230 feet, in Minnesota or Wisconsin it 

 seldom reaches 75 feet. It appears therefore that the formations thicken 

 considerably southward. 



The Shakopee below the Saint Peter is correlated with the Calciferous 

 (Beekmantown) of New York by Sardeson.^ 



The same author has described the fossils§ found in the Saint Peter 



* Geol. and Nat. Hist. Survey of Minnesota, Final Report, vol. iii, part ii, introduction. 



| American Geologist, vol. 34, no. 2, August, 1904. 



I Bull. Minn. Acad. Nat. Sci., vol. iv, no 1, p. 104. 



\ There are marine fossils in the upper part of the Saint Peter at Saint Paul, Min- 

 nesota. These have heen described by Sardeson in Bull. Minn. Acad, of Nat. Sci., vol. iii., 

 no. 3, and vol. iv, no. 1, p. 79. The following genera are represented : Cypricardites, 

 4 species ; Modiolopsis, 5 species ; Tellinomya, 2 species ; Holopea, 2 species ; Murchisonia, 

 2 species ; Ophileta, Platyceras, and Pleurotomaria, 1 species each ; Orthoceras, 3 species, 

 and one species each of Crania, Lingula, Orthis, Ptylodictya, and Rauffella. 



There were found at this place 28 species. Although nearly all described as new 

 species, they are as a whole very like the forms occurring in the overlying limestone. 

 Other localities have furnished a few forms. At Ripon, Wisconsin, in transition beds, 

 Orthoceras is found. Except fucoidal markings and Scolithus Hinnesotensis James, there 

 are no others reported from Wisconsin. 



Winchell reports Scolithus from Faribault, Minnesota, probably the same as 8. Min- 

 nesotensis James. (The Saint Peter Sandstone, Cin. Soc. Nat. Hist. Jour., 1894, p. 134.) 

 At Fountain, Minnesota, in transition beds to Stones River above, not in typical Saint 

 Peter, Lingulepsis morsensis Winchell and an Orthis resembling O. testudinaria. Piano- 

 lites is also reported from Minnesota. 



Meek refers to a Murchisonia and a crinoid column from Monteau county, Missouri ; 

 Shumard reports a Straporollus and a Chemnitzia from Ozark county, Missouri, and an 

 Orthoceras is recorded from Maries county, Missouri. 



