364 NATURAL HISTORY BULLETIN. 



shown by Calvin and his associates on the Iowa survey to be 

 a correlative of the Iowan drift, for it connects definitely with 

 the border of that drift sheet." It is a matter of some interest 

 however, that neither Professor Calvin nor his associates ever 

 considered the evidence as absolutely conclusive, and that Cal- 

 vin now holds an opinion contrary to that which this refer- 

 ence implies. 



The contention that the loess is coeval with the drift is not 

 well supported by facts in the field, and must face the objec- 

 tion that much of the loess contains numerous fossils which 

 required an abundant vegetation for their maintenance, a fact 

 which precludes glacial conditions, and that the loess and 

 drift after all occupy a definite vertical relation entirely incon- 

 sistent with contemporaneousness. Especially is there excellent 

 evidence to show that all the loess is not associated with Iowan 

 drift. Not only are there enormous deposits of loess along 

 the Missouri and the Mississippi rivers, which can in no way 

 be connected with the Iowan drift, but in the drift-border 

 areas of Iowa there is direct stratigraphic evidence (which 

 therefore ought to appeal to Mr. Leverett) that a very large 

 part of the loess is not even immediately post-Iowan. That 

 more than one loess exists in Iowa has already been shown,* 

 but during the past year so many conclusive evidences of this 

 fact have been observed by the writer that the wide extent of 

 their occurrence can no longer be questioned. A few of the 

 most striking cases are here noted. 



The Hershey Ave., exposure in Muscatine, in which there 

 is a distinct fossiliferous loess between the Kansan and the 

 Illinoisan drifts, has already been noted, as has that in section 

 20 near Davenport, in which two sharply defined loesses overlie 

 gumbo. 



A very similar section, showing only the two loesses how- 

 ever, may be seen opposite Crescent Ave., in East Davenport. 

 The loesses are separated by a well-defined oxidized band, and 

 the lower, pale bluish loess is very fossiliferous. 



*See p. 340 of this Bulletin. 



