174 THE ILLINOIS GLACIAL LOBE. 



The last three species in this list are pond species. 



" From loess in bluff above Hershey avenue, Muscatine. Iowa." (Prof. J. A. 

 Udden's note.) 



Helieiua occulta Say. 



Polygyra lnnltiliueata (Say) Pils. (Probably this species; specimen young.) 



Polygyra monodon (Rack.) Pils. 



Strebilops virgo Pils. 



Bifidaria pentodon (Say) St. 



Pupa muscorum L. 



Cochlicopa lubrica (Miill.) P. & J. 



Pyramidula altemata (Say) Pils. 



Pyramidula perspectiva t^ay) Pils. 



Pyramidula striatella (Anth.) Pils. 



Succinea obliqua Say. 



Succiuea avara Say. 



Succinea ovalis Gld. 



Limna?a caperata Say. 



Yalvata siucera Say. 



Succinea ovalis, of which one specimen was submitted, lives on mud 

 flats, etc.; Limncea caperata and Valvata sincera are pond species — the latter 

 now for the first time reported from the loess ; all the others are terrestrial 



From base of loess in bluff of Mill Creek, about 5 miles south of Milan, Illinois, 

 collected by Prof. J. A. Udden : 

 Succinea avara Say. 



Limnaea stagnalis L. A fragment, probably this species. 

 Limnsea reflexa Say. 



Plauorbis albus Miill. Not heretofore reported. 

 Plauorbis parvus Say. 

 Valvata tricarinata Say. 

 Valvata sincera Say. 

 Pisidium . Five fragments of valves, probably belonging to two species. 



With the exception of the first, all of these are pond species. 



These lists, remarks Shimek, are of special interest because of the 

 comparatively large number of pond species which they contain. The 

 presence of these forms, however, does not strengthen the aqueous theory 

 of loess formation. Both the distribution of these aquatic forms in the 

 loess and their habits in life indicate this. They do not represent the average 

 loess-fauna even of the Mississippi River, but occur in restricted areas and 

 seem to have been collected chiefly from the lower part of the loess. In 

 habits these forms are pond-inhabiting, air or water breathers, which do not 

 require or favor large bodies of water, but which flourish in smaller ponds. 



