24. Outline fairly even; shell winged posteriorly in young; umbonal mark' 



ings several fine double loops; rays (color markings) complete; nacre 

 purplish or salmon; upper Mississippi drainage 



Lampsilis leptodon (Raf.) 



Proptera (Leptodea) leptodon (Raf.) 

 Shell narrowed to a point posteriorly; not winged; umbonal markings 

 several coarse folds; rays usually broken; nacre bluish or purplish, 

 darker in the cavities; Ohio, Cumberland and Tennessee River 

 drainages 



Hemistena lata (Raf.) Twisted Shell 



Lastena lata Raf. 



25. Shell about two and one-half times as long as high, arcuate; central 



states 



Cumherlandia monodonta (Say) Spectacle Case 

 Shorter 26. 



26. Shell very evenly long'elliptical; with parallel beak markings bent up' 



wards in the middle; usually less than two inches long; central states 

 ^impsoniconcha amhigua (Say) 

 Shell more irregular; with concentric beak markings; becoming larger 27. 



27. Little indication of cardinal tubercles; ventral margin almost straight; 



umbonal markings fine; Mississippi and St. Lawrence drainages 



Anodonta ferussaciana Lea Cylindrical Paper Shell 



A.nodontoides ferussacianus (Lea) 

 Cardinal teeth represented by small tubercles or swellings of the hinge 

 line; ventral margin curved; umbonal markings coarse; generally dis' 

 tributed 



Strophitus undulatus (Say) Squaw-foot, Orange Peel 



including Strophitus rugosus (Swainson) 



28. Anterior end much narrower than the rest of the shell; rays (color 



markings) , if present, fine or inconspicuous 29. 



Anterior end not conspicuously narrow; with or without rays 30. 



29. Shell long and wedge-shaped; beaks low; nacre brownish or purple; 



western states 



Gonidea angulata (Lea) 

 Shell triangular; beaks full and high; nacre bluish; Georgia 

 Alasmidonta arcula (Lea) 



30. Posterior end flattened and corrugated; beaks elevated above the hinge 



line; rays usually broken; central states 



Decuramhis marginata (Say) Elk'toe 



Alasmidonta marginata. Say 

 Posterior end slightly or obliquely truncated; not corrugated on posterior 

 slope; beaks not much elevated; rays not usually broken 3L 



31. Posterior end obliquely truncated; epidermis dull, with wavy rays; north- 



central and eastern states 



Alasmidonta calceola (Lea) Slipper Shell 

 Posterior end slightly truncated and pinched upwards to the dorsal mar- 

 gin; epidermis shining, with narrow and wide rays, except in old shells, 

 or dull, with obscure rays 32, 



150 



