35 



ihorn color. Very abundant in tlie Fox and Illinois 

 rivers, clinging to stones, roots, etc. 



SUBFAMILY POMATIOPSIN^. 

 GENUS POMATIOPSIS, Thyox. 



l»0.nAri01»«IS I.A1»II>AKIA, Say. 



Shell turrited, thin, smooth ; volutions six ; suture 

 impressed ; aperture longitudinally ovate— orbicular, 

 operculated, rather more than one-third the length of 

 the shell ; color brown ; length one-iifth of an inch. 

 Abundant. 



This species is longer than A. porata. I follow 

 Binney in placing it in the genus Pomatiopsis. The 

 animals are amphibious, and may be found near our 

 rivers in moist places. They possess the power of 

 -crawling on the surface of the water in a reversed posi- 

 tion, shell downward. 



FA:UII.Y STKEPOW ATI ■>-!!:, II.U.de. 



This family of univalve mollusca presents in its 

 numbers and diversified forms one of the most inter- 

 esting studies in the whole range of American Con- 

 chology. There are nearly five hundred recognized 

 species of Str epiomaUdce ivom North America. Of 

 these, the larger part are from Southern waters, only 

 ii few being found in the Ohio river and its northern 

 tributaries. And these are small in size compared with 

 those from Tennessee and Alabama. In the East, the 

 St. Lawrence river and its branches form the northern 

 limit of the family ; and in the West, the northern 



