fragilis, Dunk. M. 

 glabratus, Saij. 



W. E. 

 gracilentus, GUI. W. 

 Haldemani, D. M. 

 lentus, Say. 

 Liebmanni, D. M 

 niultivolvis, Case. 

 Ne^vberryiiZm. "W. 

 obtusus, Lea. 

 opercularis, Ghl. "W. 

 planulatus, Cooper. 



"W. 

 parvus, Say. 

 regularis, Lea. 

 subcrenatus, Carp. 



W. 

 tenuis, Phil. M. 

 Traskii, Lea. W. 

 trivolvis, Say. W. E. 



(/ 



592. 



593. 

 594. 



595. 



596. 

 597. 

 598. 

 599. 

 600. 

 601. 

 602. 

 603. 

 604. 

 605. 

 606. 

 607. 

 608. 

 709. 

 610. 

 ) 



Planorbis trivolvis, Say. 



var. fallax. 

 rianorbis tuniens, Carp. 

 Planorbis tumidus, Pf. 

 Planorbis vermicularis 



W. 



M. 



aid. 

 w 



Planorbis Wheatleyi, Lea. 

 Ancylus calcarius, DeKay. 

 Ancylus crassus. Raid. "W. 

 Ancylus depressus, Ilald 

 Ancylus diaphanus, Hold. 

 Ancylus elatior, Anth. 

 Ancylus filosus, Conr. 

 Ancylus fuscus, Adam.<;. 

 Ancylus Newberryi, Lea. W. 

 Ancylus Nuttalli, Hald. MV. 

 Ancylus obscurus, Hald. 

 Ancylus parallelus, Hald. 

 Ancylus patelloides. Lea, "W 

 Ancylus rivularis. Say. 

 Ancylus tardus, Say. 



