1889.] - ^'-^ [Wlnchell. 



gToup ;" assigning as his motive the fact that ''Professor Hall, on seeing 

 the section at Kettle Pt., expressed it as his opinion that the rocks were 

 the lowest measures of the Portage and Chemung group, ' ' and the fact 

 that " a nearly complete section of the Hamilton group" had been dis- 

 covered on " some of the tributaries of the River Sable (south)." 



The ferruginous shales of the Marshall group of Michigan were again 

 pronounced Carboniferous in 1858, by Dr. R. P. Stevens.'*^ who described 

 from Battle Creek three species oiLeda and one species each of Nucula and 

 Chonetes. These are spoken of as occurring in "association with an Ortlw- 

 ceras, Nautihis, &\\6. Bellerophon Urei, which is evidently carboniferous." 



In tire same year, Professor Hall ^^ published his Report on the geology 

 of Eastern Iowa, in which he embraced the first separate account which I 

 have observed of the yellow sandstones which outcrop on the banks of the 

 Mississippi at Burlington and other localities. He speaks confidently of 

 their equivalency to the Chemung rocks of New York, and points out a 

 bed of green shale at the base, which he tliinks might represent the Por- 

 tage group. He does not fail to recognize, however, the imperceptible 

 graduation of these sandstones into the overlying Burlington limestone, 

 and expresses the opinion that the Chemung group of Missouri, as organ- 

 ized by Professor Swallow, "will probably be found to include a portion 

 of the Hamilton group. "^^ Professor Hall describes eleven species of fossils 

 from these strata, but makes no identifications with fossils from the typi- 

 cal Chemung of New York. Mr. C. A. White's "sections " of the rocks 

 at Burlington, in the appendix to this report, possess very great interest, 

 as embodying the results of exact observations. 



In September, 1860, Messrs. Meek and Worthen^^ p^xl^lished descriptions 

 of five new s^Decies of fossils from the Rockford limestone. In the same 

 month, Mr. C. A. White''s published " Observations on the Geology and 

 Paleontology of Burlington, Iowa, and its vicinity ;" embracing descrip- 

 tions of seven new species from the yellow sandstones, and elaborate 

 discussions establishing the intimate relations existing between the yellow 

 sandstones and the overlying Burlington limestone. 



During 1859-60-1, a geological survey of the lower peninsula of Michi- 

 gan was in progress under my direction. The first public announcement 

 of the determinations made upon this survey was in the foriu of a lecture 

 delivered at the University by myself to an audience consisting mainly of 

 a delegation from the Chicago Academy of Sciences, who were then on an 

 excursion to the University of Michigan. This lecture was reported in 

 full and published in the Chicago Tribune in December, 1860. A summary 

 of the results of the survey was also published in the Detroit Tribune, 

 December 11th, 1860, and briefly in the Detroit Advertiser of January 26, 

 1861. Advance sheets of my official report were sent off August 18th, 

 1861, and noticed in the American Journal of Science and Arts in Septem- 

 ber, 1861. 



■'•' Amer. Jour. Sci. [2] xxv-, 262. ''5 Geology of Iowa, 1, p. 8S. 



"« lb. p. 91. " Proo. Acad. Nat. Sci. Phil., September, 1860, p. W. 



« Jour. Boston Soc. Nat. Hist., vol. vii, p. 209. 



A. P. S. — VOL. XI — I 



