PAPERS OX GEOLOGY AND GEOGRAPHY 419 



STATIOX XO. 4, 



Locality: Bank of Du Page River, SE. V^ of SW. i^, 

 Sec. 16, T. 35 X., R. 9 E. 

 Material : Alluvial clay. 

 Stratigraphic horizon: Pre-recent. 



MOLLUSCAX LITE 



Goniohasis livescens Meiike, common. 



Valvata tricarinata Say, rare. 



Sphaerium stamineum (Conrad), common. 



Planorbis trivolvis Say, rare. 



Planorhis antrosus Conrad, rare. 



Planorbis crista Linn., rare. 



Polygyra thyroides (Say), rare, young. 



This is a river fanna and is of the same general charac- 

 ter as the river fauna of today in this region. The sin- 

 gle specimen of Planorhis crista is peculiar in lacking 

 the ribs ^vhich are characteristic of that species. This 

 is the only specimen of this form observed among hun- 

 dreds of specimens examined, both recent and fossil. 



STATIOX XO. 6. 



Locality: SW. end of southern slough, NW. i/4 of SE. 

 1^, Sec. 11, T. 35 N., R. 9 E. 

 Material: Alluvial clay. 

 Stratigraphic horizon : Pre-recent. 



MOLLUSCAX LIFE 



Planorhis campanulatus Say, rare, but one broken 

 specimen found. 



Planorhis antrosus Conrad, rare, one immature 

 specimen. 



Planorhis deflect us Say, common, the keeled peri- 

 phery not as acute as in some recent forms. 



Planorhis exacuous Say, not common, and typical. 



Planorhis crista Linn., not common, -^ith sharp, well 

 defined ribs. 



Planorhis altissimus Baker, abundant, somewhat 

 resembling some forms of parvus. 



Amnicola lustrica Pilsbry, rare and typical. 



