CHECK LIST 



—OF— 



North American Naiades. 



I. 



SYSTEMATIC ARRANGEMENT. 



fam;ly unionid.^ 



Sub-Family Unionin.^ Swainson 



EXOBRANCHI^. 



HETEROGEN^. 



Genus Truncilla Rafinesque. 

 Subgenus Truncilla Rafinesque. 



1. Group of TruHcilla triquetra. 



2. " " " hrevidens.. 



3. " " " arcaeformis. 

 Subgenus ScalEnaria Rafinesque. 



^4. Group oi Truncilla sulcata. 



5. " " " haysiana. 

 Subgenus Dysnomia Agassiz. 



6. Group oi Truncilla foliata. 

 Subgenus Pilea Simpson. 



7. Group of TmnciUa personata. 



8. " " " perplexa. 



Genus MiCROMYA Agassiz. 



1. Group of Micromya fahalis. 



2. " " " cczlata. 



