LOESS FOSSILS. Jg7 



The Davenport fossils are apparently from the unmodified loess along 

 the west bluff of the Mississippi, as are also those from Burlington, Iowa. 

 The list from Moline, Illinois, is from specimens gathered on the level upland 

 lying between the Rock and Mississippi rivers. A loess-like silt carrying 

 fossils has been found beneath the glacial deposits in that vicinity. The 

 fossils, so far as identified in this lower silt, are strikingly similar to those 

 found in the surface deposit. 



The list from Muscatine, Iowa, contains, in addition to the usual loess 

 fauna, several species of Unio. Unfortunately the evidence is not clear 

 concerning the condition of the bed of loess in which these Unio shells was 

 found. It is Professor Witter's present opinion that the loess had suffered 

 some disturbance, thus leaving it an open question whether the shells are as 

 ancient as that deposit. 



The fossils noted in the list from near Freeport are stated by Hershey 

 to have been secured from under a bed of loess in a blue-green silt, 

 separating the loess from the underlying gravel. He further states that the 

 gravel is made up in part of erratics, and is, therefore, not preglacial in age. 

 This gravel and the overlying silt are described by Hershey under the 

 name "Florencia formation," 1 and are referred to an interglacial stage 

 between the loess deposition (which he correlates with the Iowan glaciation) 

 and a preceding period of glaciation now provisionally referred to the 

 Illinoian. It is stated that great care was taken in securing the shells, 

 because it was early recognized that a fauna of very similar facies occurs in 

 the modern alluvial deposits of that region. It is also stated that this blue-- 

 green silt is overlain with perfect conformity by the basal member of the 

 Iowan loess series, a feature which leads the present writer to question 

 whether it should be separated from the loess series. However, the striking 

 contrast between the fauna of this deposit and that usually displayed by the 

 loess and the striking similarity to the alluvial fauna of that region, should 

 have weight in determining the classification. 



The list from Virginia, Illinois, is made up entirely of a collection in 

 the office of Dr. J. F. Snyder, at Virginia, who also made the identifications. 



'Amer. Jour. Sci., 4th series, Vol. IV, 1897, pp. 90-98. 



