NOMENCLATURE 183 



was paid to the application of names to the several parts of the Galena 

 and also of the Maquoketa series. N. H. Winchell and E. 0. Ulrich* at 

 the same time adopted a very similar stratigraphic and paleontologic 

 scale as my own for Minnesota, and they correlate not merely with Wis- 

 consin, but adopt the formational names Stones Eiver and Black Kiver 

 from more distant regions, instead of using the name Trenton limestone, 

 this last name in turn being used instead of the term Galena limestone. 



Without attempting to repeat to any extent the evidence as it appears 

 in the cited articles concerning the two formations now under discussion, 

 I may say in brief that the extent, uniformity of thickness, evident orig- 

 inal petrographic equality, and, above all, the evidence of persisting or 

 coextensive faunal zones, marked in particular by certain migrations of 

 species over the entire province, show that practically the same strata ex- 

 tend over the area of the Galena-Trenton in the four states already 

 named. It is further evident that when a geologist adds to the knowl- 

 edge of these formations in one part of the area, that knowledge extends 

 also to other parts, and that likewise the nomenclature of the formations 

 requires uniformity for the entire area. 



Nomenclature 



In spite of the local petrographic diversity, the same two formational 

 names of Trenton and Galena have been employed over the entire area 

 in the several states. This continuance or seeming uniformity of nomen- 

 clature may of course have been aided largely by the Saint Peter sand- 

 stone's sharp contact under the "Trenton" and the contrast of the Maquo- 

 keta shales upon the Galena, whereby the stratigraphic equivalence ap- 

 pears doubly evident. That the aid of the contrasting lithologic charac- 

 ters of subjacent and superjacent formations has been relied on by au- 

 thors is indicated when we find that in northern Iowa and southern 

 Minnesota, where the overlying Maquoketa is rather a limestone than a 

 clay formation, there the nomenclature has been least conformable in its 

 application. In Alamakee county, Iowa,f the shaly bed at the top of 

 the Galena was sometimes passed over or overlooked and the term Galena 

 was applied to the Maquoketa limestone, since it looks like the Galena 

 lithologically. 



Again, in southern Minnesota a shaly bed really belonging to the 

 Galena stratigraphically is called Maquoketa in official reports, J and the 



* Geol. and Nat. Hist. Surv. Minn., Final Kept., vol. iii, 1806, pt. 2, p. Ixxxiii. 

 t Iowa Geological Survey, vol. Iv, 1895, p. 80. 



+ Vide Geol. and Nat. Hist. Survey of Minnesota, vol. iii, pt. I, p. 1. "Names used 

 in the Minnesota Reports, 1872-1892." 



