74 AN ANNOTATED CATALOGUE 



ill abundance living near Iowa City, and later in Hardin 

 county. Its distribution at Iowa City is very peculiar, and 

 very limited in extent. The locality is on Turkey creek 

 four miles north of Iowa City. It is a steep hillside on the 

 south side of the creek, and covered with a dense growth 

 of ferns and other plants. Here confined within an area 

 scarcely forty yards in extent this little species flourishes 

 so abundantly that several hundreds have been collected in 

 a short time. Beyond this little secluded spot not a sin- 

 gle specimen is found living, except in Hardin county 

 where numbers have been collected in a similar situation. 

 This species is one of the most abundant and characteris- 

 tic fossils of the loss. 



Family Strepomatid^. 



Pleurocer^a subulare Lea. This species as also P. lewisi 

 which is very closely allied if not identical, is found abun- 

 dantly in the Iowa river where it is usually attached to 

 stones in shallow water. It occurs quite commonly in the 

 muddy bed of the Minnesota river about Ft. Snelling. In 

 central Iowa "dead" shells are common along the streams 

 but as yet living ones have not been found. 



Goniohasis cubucoides Anthony. This species occurs 

 abundantly in the Raccoon river in Dallas county. 



LAMELLIBRANCHIATA. 



Family Corbiculadye. 



Sjjhcerium stamineum Conrad. Common, but not as 

 generally distributed as the next. 



/Sphoeriuin strialinum Lamarck. Abundant everywhere 

 in creeks and rivers. 



8ph(£rium rhomboideum Say. Common in some local- 

 ities ; rare in others. 



