110 



GEiOIvOGY OJ" IvA SAIvLi: COUNTY. 



We sometimes find a shell corresponding- to Pahi- 

 dina heterostropha, Kirtland. The shell is sinistral, 

 has five whirls, stiture is distinct, color g-reen, leng-th 

 three-fourths of an inch. Loc. Fox river. The shell 

 has been referred by authors to various species as only 

 a reversed variety, and I am inclined to so consider it. 



Melantho subsolidus, Anthony. — Shell ovate, 

 thick, whirls six, suture distinct, aperture ovate, spire 

 elevated, apex entire, color g-reen, leng-th one and one- 

 half inches. Abundant. 



One of our most abundant species; considered by 

 some a synonym of M. decisus. Very variable in its 

 characters. 



GENUS IvIOPI^AX, TROSCHi:rv. 



Lioplax subcarinata. Say. — Shell has six carinated 

 whirls, wrinkled, suture impressed, aperture oval, 

 color g-reenish, leng-th three-fourths of an inch. Loc. 

 Illinois river. 



Say's description of this species was of a dwarfed 

 specimen and represents it as having- but three whirls. 

 We have M. coarctata. Lea, and M. riifiis, Halde, 

 specimens not abundant. There remains much work 

 to be done before the true position of some species 

 is determined. 



FAMILY RISSOID^ — SUBFAMIIvY HYDROBIN^— GENUS 

 AMNICOEA, G. & H. 



Amnicola porata. Say. — Shell obtuse, conic, volu- 

 tions four, wrinkled, spire obtuse, labrum and labium 

 equally rounded, umbilicus distinct, shell rather short, 

 horn color. Very abundant in the Fox and Illinois 

 rivers, cling-ing- to stones, roots, etc. 



