OF THE MOLLUSCA OF IOWA. 65 



remarkable examples of the former are illustrative of the 

 severe injuries that these inollusks may receive and yet sur- 

 vive, and even attain a normal size, while of the latter group 

 of abnormalties the transposition of the teeth in the valves 

 of Unio is perhaps the most notable ; and probably arises 

 from the same peculiar embryonal conditions that have 

 produced dextral shells among sinistral univalves and vice 

 versa. 



Thanks are tendered Prof. R. E. Call for the verification 

 of some of the Uniones. 



GASTEROPODA. 

 Family Selenitid^, 

 Macrocydis concava Say. Iowa City ; rather common ; 

 Muscatine, Burlington and other localities in eastern Iowa. 

 The distribution of this species is chiefly east of the Mis- 

 sissippi river ; its western limit being the eastern portions 

 of Iowa and Missouri. 



Family LiMACiDiE. 



Limax campesiris Binn. Des Moines, Iowa City, Bon- 

 aparte : abundant. A widely distributed species, and 

 doubtless occurs throughout the state. 



Zonites arboreus Say. Abundant everywhere. 



Zonites nitidus Miiller. The only locality in Iowa from 

 which this species has been obtained is Hardin county. 



Zonites viridulus Menke. Northern and eastern Iowa : 

 rather common. 



Zonites indebitatus Say. Iowa city is the only locality 

 in the state where this species has been collected. 



Zonites minuscidus Binney. Johnson, Scott and Mus- 

 catine counties : quite common. 



ZomVes /m?vms Draparnaud. Eastern Iowa: not com- 

 mon. The six species of zonites here enumerated all have 



