PLATE 2 - continued 



Figs. AA, BB. - Pisidium varlnb He Prime; interior and exterior views of right valve, 

 respectively. Farmdalian water-laid silts, Wedron Quarry section, SEj SE^ 

 SW{ sec. 9, T. 34 N., R. 4 E., La Salle County. Enlarged approximately 

 6X. 



Fig. CC. - Lymnaea palustris (Miiller); apertural view. Farmdalian water-laid silts, 

 Lake Bloomington Spillway section, SW^ NE{ sec. 1, T.25N., R. 2E., 

 McLean County. Enlarged approximately 2X. 



Figs. DD, EE. - Sphaerlum occidentale Prime; interior and exterior views of right 

 valve, respectively. Basal zone Peoria loess, SE^ SW| sec. 26, T. 4 N., 

 R. 3 E., Fulton County. Enlarged approximately 3|X. 



Figs. FF, GG . - Pisidium caseratanum (Polis); interior and exterior views of right 

 valve, respectively. Farmdalian water-laid silts, Wedron Quarry section, 

 SE| SE| SW{ sec. 9, T. 34 N., R. 4 E., La Salle County. Enlarged approx- 

 imately 3jX. 



Figs. HH, II, LL. - Helisoma trivolvis (Say); umbilical, spiral, and apertural 



views, respectively. Basal zone Peoria loess, SE| SW| sec. 26, T. 4 N., 

 R. 3 E., Fulton County. Enlarged approximately 2 1/3X. 



Figs. JJ, KK. - Sphaerium striatinum (Lamarck); interior and exterior views of right 

 valve, respectively. Basal zone Peoria loess, SE{ SW| sec. 26, T. 4 N., 

 R. 3 E., Fulton County. Enlarged approximately 2X. 



Figs. MM, NN, OO. - Helisoma antrosa (Conrad); umbilical, apertural, and 



spiral views, respectively. Farmdalian water-laid silts, Wedron Quarry 

 section, SE} SE} SW{ sec. 9, T. 34 N., R. 4 E., La Salle County. En- 

 larged approximately 2^X. 



"161 



