The Mollusc a of Eastern Iowa. 77 



U. PUSTULATUs. — Lea. 



Not common; in the Mississippi. 

 U. PUSTULosus. — Lea. 



Very common. Sometimes rayed. Pustules often entirely 

 wanting. Found in all the tributaries of the Mississippi in 

 this state. This is the same as U. schoolcraftii. The latter 

 is not even a distinct, constant variety. 

 U. PYRAMiDATUS. — Lea. 



Reported from the Mississippi. Scarcely a good species. 

 U. RECTUS. — Lam. 



Common in the Mississippi drainage. Nacre often almost 

 white. The young are rayed. 

 U. RUBiGiNOsus. — Lea. 



Rather common. Found in the Mississippi, Des Moines, 

 Skunk, Iowa, Cedar and Shell Rock rivers. Specimens from 

 the Skunk river are particularly fine. 

 U. SECURis. — Lea. 



Common in the Mississippi. Rare in the Cedar and Iowa 

 rivers. 



U. soLiDus. — Lea. 



Reported from this state. Scarcely a good species. 

 U. SPATULATUS. — Lca. 



Very common in portions of the Iowa and Cedar rivers, 

 especially in mud among stones. Nearly all are distinctly 

 rayed. 



U. SUBROSTRATUS. — Say. 



Very common in ponds, creeks, etc., near Iowa City and 

 along the Mississippi. This is commonly called U. missis- 

 si^fiensis. 



U. TENUissiMus. — Lea. 



Rather rare. We collected probably one hundred speci- 

 mens at Cedar Rapids and Iowa City. This species shows 

 clearly the insufficiency of the characters of the genera 



