C. A. White on Drift phenomena in S.W. Iowa. 308 
cS. . . 
currents over this part of the continent, but the coincidence of 
the direction of those scratches which have been observed with 
the existence of the important lacustrine deposit there. The 
close of the Drift period evidently left a large depression of the 
Tiver if it were possible to throw a permanent obstruction across 
prmeipally Gasteropods, are often found in this deposit, from 
ase to top, and its thickness sometimes reaches more than two 
