390 IOWA ACADEMY OF SCIENCE Vol. XXVI, 1919 



loesses of the upper Mississippi valley. At some places it is in the 

 lower, gray loess, at some in the upper, yellow loess, and at others 

 in both, in the same exposure. 



In all discussions of this species it must be borne in mind that it 

 is strictly a deep-woods form. Where loess accumulated on the 

 prairies it contains no fossils of this species, and so far as we can 

 judge from the habits of the living representatives, its presence is 

 conclusive evidence of well-developed forest conditions. 



Department of Botany^ 

 The State University. 



