HISTORIC RESUME. 169 



on tlie various jiages cited. Paleontologic notes also found there state 

 that " some seaweeds, a few molhisks, an occasional fragment of a trilo- 

 bite and a few obscure forms make up the meager list of fossils " which 

 could with certainty be referred to this, the Mendota, limestone.'^ 



In Iowa the lower Magnesian limestone has been noted in the north- 

 eastern portion of the State. It is most consi)icuous along the upper 

 Iowa river and in tlie valleys of Paint creek and Yellow river.f The 

 thickest beds were 2')0 feet; the variations in texture and color were re- 

 ported as considerable; the chemical composition varied but little from 

 that of a juire dolomite ; its brecciated and concretionary character was 

 noted as a principal feature, and no fossils were found in the formation 

 within the limits of Iowa. Twelve years later, however, Dr C. A. AVhite 

 stated that a few traces of the stems of crinoids had been found near 

 McGregor. They were so fragmentary and indistinct that no identifica- 

 tion of them could be made; also some traces of 2:>ossible fucoids were 

 found. J 



Recently W J McGee has very pointedly discussed the nomenclature 

 of this series for Iowa§ and for the broader northwest. || 



In the past year Professor Calvin, state geologist of Iowa, has noted 

 the discovery of a fauna which leaves little doubt of the exact equivalence 

 of the lower Magnesian limestone of Iowa and the Calciferous series of 

 northeastern New York.^ 



During the last two seasons, having gone over the ground in Minne- 

 sota more thoroughl}' and critically and having extended their studies 

 into the adjoining states of AVisconsin and Iowa, the authors desire to 

 discuss certain phases of the Magnesian series which were barely touched 

 upon in their former paper. Those phases are partly stratigraphic and 

 paleontologic and partly lithologic and genetic. 



Members of the Series. 



order of occurrence and thickness. 



The Magnesian series consists of five formations, namely, tliree doio- 

 mites and dolomitic shales and two silicious sandstones. Enumerated in 

 ascending order, they are: 1, the Saint I^awrence dolomites and shales ; 

 2, the Jordan sandstone ; 3, the Oneota dolomite ; 4, the New Richmond 



• Ibid., vol. i, p. 141. 



tOeology of Iowa, Jnmes Hall, state geologist, vol. i, 18').S, part 1, p. 3.32. 

 JCieoloKV of Iowa, Charles A. White, state goolovrist, vol. i, l«7ii, p. 171. 



?WJM«-«;ee: The Pleistocene History of Xortli.iasicrn Iowa, Kl.v.ntli Aim. K-p. T. S. (i.-oj. 

 Survey, 1889-'9<», pp. 187-577. 



I Bull. Geol. Soc. Am., vol. 3, 1892, p. 4f)t. 



1 American Geologi.st, Minneapoli.s, vol. x, 18'j2, pp. H 1-118. 



