514 UNITED STATES GEOLOGICAL SUEVEY OP THE TERRITORIES. 



3. naidea, Swainson. 



Shell not winged, obovate; surface of valves smooth. — (JJnio 

 amygdalum, Lea.) 



4. obovaria, Raf. (— Rhipidodonta, Morch). 



Shell not winged, subrotund; surface of valves smooth. — (Unio 

 circulus, Lea.) 



5. NxasA, Swainson. 



Shell not winged, oblong; surface of valves smooth. — (Unio 

 depressus, Lamarck.) 



6. hyridella, Swainson. 



Shell not winged, oval; surface of valves smooth. — (Unio Bata- 

 vus, Lamarck.) 



7. lampsilis, Raf. (— Truncilla, Pleurobema, Syntoxia. Scalenaria, and 



Plagiola, Raf; Crenodonta, Schltit. ; and jEglia, Swain- 

 son). 

 Shell not winged, more or less triangular or oblique, and trun- 

 cate at one end ; surface of valves smooth. — (Unio trigonus, Lea.) 



8. canthyria, Swainson. 



Shell not winged, subtrigonal ; surface of valves spiniferous ; 

 cardinal teeth long, compressed. — ( Unio spinosus, Lea.) 



9. iridea, Swainson (— Tritigonia and Orthonymus, Agassiz). 



Shell not winged, wide; surface of valves nodulous. — (Unio 

 cylindricus, Say.) 



10. rotundaria Raf (— Cyprogenia, Agassiz). 



Shell uot winged, subrotund or oblique ; surface of valves nodu- 

 lous. — (Unio nodulosus, Wood.) 



11. quadrtjla, Raf. (= Theliderma, Swainson). 



Shell not winged, quadrate or triangular; surface of valves 

 tuberculated. — (Unio apicidatus, Say.) 



12. diplodon, Spix (=: Cucumaria, Conrad, and Naia, Swainson). 



Shell not winged, oval or oblong ; surface of valves plicated. — 

 (Unio eUipticus, Spix.) 



13. dysnomy a, Agassiz. 



Shell not winged, quadrate or triangular ; surface of valves 

 plicated. — (Unio atrocostatus, Lea.) 



