3 go Quarterly Journal of ConcJwIogy. 



I have specimens of graiidis nearly 20 cm. long 

 Shells thin, as all our pond bivalves are. 

 A. EDENTULA, Say, Common; Mississippi river. 



A. FERUSSACiANA, Lea. Very rare here. I have found dead 

 shells along the Mad Creek, but no live one here. 



I have good specimens from Honey Creek, Delaware 

 County, Iowa. 



A. iMBECiLis, Say. Abundant in all our sloughs. 



A. SUBORBICULATA, Say. Common in Keokuk Lake; a fine but 

 fragile shell. This lake is the expansion of Muscatine 

 Slough, a body of water formerly connected Avith the 

 Mississippi river on the Iowa side in thi? city, winding 

 away from the river 4-5 miles, and widening some 4 miles 

 S.W. of us into Keokuk Lake, and at a distance of about 

 18 miles reaches the river again. The lake is 4-5 feet 

 deep, about 2 miles long and i mile wide, largely filled 

 Avith Nelumbium luteum. 



Margaritana complanata, Barnes. Common; Mississippi river, 

 and sloughs connected therewith, DesMoines river, Mud 

 Creek, &c. 



M. CONFRAGOSA, Lea. Very rare; Mississippi rivei-, DesMoines 

 river. 



M. MARGINATA, Say. Rare; Mississipi and DesMoines. 



M. RUGOSA, Barnes. Rare; Mississippi and DesMoines. 



M. DELTOiDEA, Rare. I find dead shells with Auodouta fcr- 

 ussacia7ia along Mad Creek, and it is found in Honey 

 Creek with the same Auodonta. I have not found it alive. 



Unio ^sopus, Green. Abundant; Mississippi river and DesMoines. 

 Shell thick, light color. 



U. ALATUS, Say. Common; Mississippi. Young shells are hand- 

 some; interior fine nacreous purple. We have a var. 

 somewhat rare, much heavier, longer, little or no dorsal wing. 



