89. Umbonal markings three irregular nodulous ridges; beaks full; nacre 



salmon to purple; usually less than one and one-half inches long; east' 

 central states 



Carunculina gJans (Lea) Purple Lilliput Shell 

 Umbonal markings five or more sharp ridges turned up behind; beaks 

 moderate to low; nacre white, bluish or salmon; becoming two inches 

 long; east'central and central states 



Carunculina parva (Barnes) Lilliput Shell 



90. With a low posterior ridge sloping toward the postbasal angle 9L 

 Shell more evenly rounded or pointed behind 94. 



9L Beak cavity impressed; usually with faint wavy rays; New York to 

 North Dakota and south to Ohio 



Lampsilis elUpsifonms (Conrad) Ellipse 

 Actmonaias ellipsiformis (Conrad) 

 Beak cavity shallow; rays often obscure 92. 



92. No interdentum; beak markings several concentric loops drawn together 



and curved up behind; central states 

 Elliptio tetralasmus (Say) 

 Unwmerus tetralasmus (Say) 

 With an interdentum; beak markings not so 93. 



93. Epidermis usually dark; nacre usually purplish; Atlantic drainage 



Elliptio complanatus (Dillwyn) Spike 

 Epidermis usually tawny; nacre white; east'central states 

 Ptychohrayichus fasciolare (Raf.) Kidney Shell 



94. Epidermis and nacre both shining; epidermis usually brightly rayed; 



greatest height usually through the end of the laterals, with the shell 



often swollen in this region 95. 



Epidermis usually rather dull; shell not higher posteriorly 97. 



95. Rays usually broken; shell thin and small 



Lampsilis nervosa (Raf.) Rainbow Shell 

 Ivlicromya iris (Lea) 

 Rays often wavy; shell moderate; becoming large 96. 



96. Nacre thickened anteriorly; nacre white or pink; posterior slope round' 



ed; east'central and central states 



Lampsilis fasciata (Raf.) Fat Mucket 

 Lanips-iUs siliquoidea (Barnes) 

 (Lampsihs luteola (Lamarck) ) 

 Nacre not much thickened anteriorly; nacre silvery, often bluish or 

 brown in cavities; posterior slope slightly flattened; south-central states 

 Lampsilis fasciata hydiana (Lea) Southern Fat Mucket 

 Lampsilis hydiana (Lea) 



97. Teeth small and delicate; epidermis dull, with many rays; nacre dull, 



often tinged with salmon or purple; valves very shallow; Atlantic 

 drainage 



Lampsilis radiata (Gmelin) Eastern Mucket 

 Teeth fairly solid; epidermis dull, with obscure and often faintly inter' 

 rupted rays; nacre white or pink; valves only moderately shallow; 

 Mississippi drainage 



160 



