558 Shells in Massaehnsetts. 



III. GENUS ANADONTA, Lam. 



Anadonta. 



cataracta, Say. Common Green Muscle, 

 marginata, Say. Blackstone and French Rivers, 

 lugubris, Say. Ponds in Essex Co. 



IV. GENUS CYCLAS. 



Cyclas. 



similis, Say. 

 dubia,* Say. 



And two species not described. 



II. UNIVALVES. 



I. GENUS PALUDINA. 



Paludiria. 



decisa, Say. 

 limosa? Say. 



II. GENUS PLANORB1S. 



Plariorbis. 



trivolvis, Say. 

 bicarinatus, Say. 

 armigerus, Say. 

 campanulatus. 

 parvus, Say. 



III. GENUS LYMNABA. 



Lymnaea. 



catascopium, Say. 

 heterostropha, Say. 

 coluinella, Say. 



And one species not ascertained. 



LAND SHELLS. 



IV. GENUS HELIX. 



Helix. 



alaboris. Common Wood Snail. 



arboreus, Say. 



trident ata, Say. 



alter nata, Say. 



glaphyra, Say. 



thypopdus, Say. 



minuta, Say. 



hirsuta, Say. 



* This does not agree exactly with my specimens of the dubia found in 

 Pennsylvania, but I think it not sufficiently distinct to be separated from that 

 species. 



