8o Natural History Bulletin. 



A. DECORA. — Lea. 



Found in mud in sluggish streams. We have specimens 

 from the Cedar and Iowa rivers and from several of their 

 tributaries. 



A. GRANDIS. — Say. 



Specimens referable to this species have been found at sev- 

 eral points. 

 A. ovata(?) — Lea. 



Specimens which were referred to this species by Prof. Call 

 were found at Cedar Rapids. 

 A. PLANA — Lea, 



Common in the Iowa, Skunk, Cedar and other eastern and 

 central streams. 



While in accordance with a common custom we list the five 

 preceding forms as distinct species, we believe that they are 

 mere modifications produced by environment to some extent, 

 though certainly not entirely, for from a series obtained at one 

 time from the same place we have been able to select at least 

 three of the above species ( ?) which however were connected 

 by an unbroken chain of intermediate forms. They should not 

 even rank as varieties. We list them simply to indicate some- 

 thing of the variation of A. grandis (to which we think all are 

 referable), in this state. It is a deplorable fact that many con- 

 chologists who rigidly draw the line excluding useless syno- 

 nyms in some groups of Mollusca, still give their imaginations 

 (for it does require a wonderfully vivid imagination to 

 identify some of the Anodontas) full sway when they treat of 

 this crenus. 



o 



A. edentula. — 6«y. 



Not uncommon in the larger streams with Marg. rugosa 

 Unio spatiilatus, etc. 

 A. PAvoNiA. — Lea. 



Specimens agreeing in every particular with those received 

 from Ohio and other eastern slates, occur commonly at Iowa 



