114 KANSAS UNIVERSITY SCIENCE BULLETIN. 



which reached its climax in the southern extension of the 

 glaciers to northern Kansas, and still later, of course, the 

 former conditions have returned. 



PLEISTOCENE OF THE REGION. 



To the Pleistocene we refer a large number of shell-bearing 

 deposits found all the way along Prairie Dog creek between 

 Norton and the Republican river. Some of the deposits are 

 of uniform consistency throughout and seem to be of aerial 

 origin, while others are distinctly laminated and contain some 

 gravel and nodules of white disintegrated Miocene rock, indi- 

 cating that they are of fresh-water origin. 



One mile east of Long Island the bed of the creek is formed 

 of a comparatively tough green marl, which contains an 

 abundance of fossil shells. The creek has cut down through 

 this marl, which is not all of the same consistency, for a dis- 

 tance of thirty feet. Shells are scattered all through this, 

 except in the upper ten feet. The marl seems unmistakably 

 of fresh-water origin, and most of the fresh-water species 

 were found in it. 



West of Long Island about three miles there is an exposure 

 of about twenty feet of sand lying on top of Miocene shales, 

 which form the bed of the creek. The deposit contains an 

 abundance of shells, but owing to the few Lymmeas found, and 

 structure of the whole, it is supposed to be of wind origin. 

 This deposit was the only one seen which had the columnar 

 structure of the Mississippi and Missouri river valleys. Along 

 the latter streams the loess exists as a chain of hills along the 

 banks of the streams, but if such a condition ever existed 

 along Prairie Dog creek, erosion has eliminated all traces of it. 

 The deposit under consideration could have been drifted by 

 the wind, owing to the position of the surrounding Miocene 

 hills. 



The species found in the deposits, which seem to be of wind 

 formation, are, with the exception of most of the fresh-water 

 ones, the same as those found in the marl east of Long Island. 

 The latter is of undoubted water origin, and all seem to be of 

 contemporaneous deposition. 



In the loess of the Mississippi and Missouri river banks 

 there are an abundance of fossils belonging to species, with 

 one or two exceptions, exactly the same as inhabit the region 

 at the present time. They have lived in the locality ever 



