13 



575. 

 576. 



577. 

 578. 

 579. 

 580. 

 581. 

 582. 

 583. 

 584. 

 585. 



586. 

 587. 

 588. 



589. 

 590. 

 591. 



Piano rbis 

 Planorbis 



Planorbis 

 Planorbis 

 Planorbis 

 Planorbis 

 Planorbis 

 Planorbis 

 Planorbis 

 Planorbis 

 Flanorbis 



Planorbis 

 Planorbis 

 Planorbis 



Planorbis 

 Planorbis 

 Planorbis 



fragilis, Dunk. M. 

 glabratus, Say. 



W. E. 



gracilentus, Gld. W. 

 Haldemani, D. M. 

 lentus, Say. 

 Liebmamii, D. M 

 multivolvis, Case. 

 Newberryi,.Lea. W. 

 obtusus, Lea. 

 opercularis, Gld. W. 

 planulatus, Cooper. 



w. 



parvus, Say. 

 regularis, Lea. 

 subcrenatus, Carp. 



* W. 



tenuis, Phil. M. 

 Traskii, Lea. W. 

 trivolvis, Say. W. E. 



592. Planorbis trivolvis, Say. 



var. fallax. 



593. I-lanorbis tumens, Carp. W. 



594. Planorbis tumidus, Pf. M. 



595. Planorbis vermicularis, Gld. 



W 



596. Planorbis Wheatleyi, Lea. 



597. Ancylus calcarius, DeKay. 



598. Ancylus crassus, Hald. W. 



599. Ancylus depressus, Hald 



600. Ancylus diaphanus, IMd. 



601. Ancylus elatior, Anth. 



602. Ancylus filosus, Conr. 



603. Ancylus fuscus, Adams. 



604. Ancylus Newberryi, Lea, W. 



605. Ancylus Nuttalli, Hald. W. 



606. Ancylus obscurus, Hald. 



607. Ancylus parallelus, Hald. 



608. Ancylus patelloides, Lea. W 

 709. Ancylus rivularis, Say. 



610. Ancylus tardus, Say. 



