118 IOWA ACADEMY OF SCIENCE 



section Prof. E. M. Shepard's recognition 18 of the Chouteau, 

 Hannibal and Louisiana members also seems to be fully sub- 

 stantiated by recent observations. Still later Prof. Stuart 

 "Weller, 19 from a critical study of the fossils found in the so- 

 called Northview sandstone (Hannibal), furnishes indubitable 

 evidence in support of the early interpretations. By showing 

 the identity of the Northview fauna with that of the beds lying 

 immediately beneath the Burlington limestone at Burlington, 

 Iowa, correlation with the Hannibal shale seems complete. At 

 Burlington the latter are known to cover the interval of fifty 

 feet between the base of the Burlington limestone and the hori- 

 zon of the Louisiania limestone. 20 



The correlation of the original Chouteau limestone with the 

 recently proposed Fern Glen formation, twenty miles west of 

 St. Louis, presents many uncertainties. South of the Missouri 

 river the lowermost Burlington limestones lose their character- 

 istic lithologic features. They no longer remain crinoidal breccias. 

 Texturally they strongly resemble the typical Chouteau and Lou- 

 isiana limestones. The red coloration, so conspicuous northward 

 at Burlington city, persists. As described in detail by Professor 

 Weller 21 the fauna appears to be identical Avith that of the red 

 Burlington beds occupying the lower twenty to thirty feet of the 

 Iowa section. Aside from a few weeks 7 collecting in the typical 

 Lower Burlington strata, by the late Doctor Wachsmuth and my- 

 self, no crinoids of consequence have been obtained at Burling- 

 ton in forty years, so that the determination of the zonal distri- 

 bution of these forms has not been recently possible. The figures 

 of the Fern Glen fossils seem to represent leading species which 

 Niles and "Wachsmuth 22 long ago listed as characterizing their 

 Lower Burlington division of the Iowa section. These facts are 

 admirably brought out by Professor Weller 23 in his late discus- 

 sion of the affinities of the Fern Glen faunas. 



ls Ibid., Vol. XII, p. 49, 1898. 

 "Journal of Geology, Vol. JX, p. 130, 1901. 

 "Am. Jour. Sci.. (4), Vol. XXXVI, p. 161, 1913. 

 ^Geol. Sue. America, Vol. XX, p. 265, 191)0. 

 -Am. Jour. Sci., (2), Vol. XLII, p. 95, 1866. 

 ^Bull. Geol. Soc. America, Vol. XX. p. 265, 1909. 



