24 IOWA ACADEMY OF SCIENCES. 



seems to occupy. Lithologically and paleoutologically the fossiliferous beds 

 resting on these limestones at Davenport, referred by Barris to the Cornifer- 

 ous, ai-e believed to be equivalent to the Oypidula occidentalis and Rhyncho- 

 nella intermedia limestone, whose presence defines the third stage of the 

 breccia in Linn county, and which in Buchanan county has been named the 

 Gyroceras beds. At Davenport, as in the counties to the northwest, the 

 Gyroceras beds are succeeded by a soft, shaly limestone with a character- 

 istic fauna. 



The writer has felt the need of definite terms to designate these beds, 

 and therefore suggests for the consideration of workers in this field the 

 name. Lower Daveniyort beds for the lower unfossiliferous limestone at 

 Davenport, the limestone which furnished the fragments for the second 

 stage of the Fayette breccia. If a geographical as well a paleontological 

 term should be found convenient for the fossiliferous limestone overlying 

 these lower beds, the term Upper Davenport beds could be appropriately 

 used as a synonym of the Gyroceras beds. 



The change in fauna is so distinct at the summit of the Gyroceras beds 

 that it seems to the writer that they should be separated from the Cedar 

 Valley limestones, as the Independence shales have been. 



If the inferences we have drawn are correct, the "Upper Helderberg" of 

 Hall, and the "Cornifei-ous" of Barris, at Davenport, are superior to the 

 hox-izon of the Independence shales. They must therefore be included in 

 that broad biotic unity whose termini are the Independence shales and the 

 Lime creek shales, whose fauna have been shown by Calvin to be so similar. 



It is an interesting fact that the new Devonian terrane, the Otis beds, 

 found beneath the Independence shales, contains, as we have stated, as its 

 characteristic fossil a Hamilton and Chemung species, and carries no 

 species, so far as known, allied to pre-Harailton faunas in other states. 



Geological Laboratory of Cornell College, December 28, 1893. 



CRETACEOUS FORMATIONS OF NORTHWESTERN IOWA. 



BY CHARLES K. KEYES. 



{Abstract.) 



Until recently little definite information has been accessible concerning 

 the distribution and subdivisions of the Cretaceous deposits of Northwestern 

 Iowa. Strata of Cretaceous age have been recognized from time to time at 

 various points, but, as a rule, little detailed information has been recorded. 

 As early as 1840 Nicollet called attention to certain sections near the mouth 

 of the Sioux river which he regarded as Cretaceous in age. Since that 

 time Cappellini, Marcou, Meek, Hayden, White and others have been 

 through this region. In all these cases the rocks noted were in the imme- 

 diate vicinity of the Missouri river. White gave more attention, perhaps, to 



