2l8 THE AMERICAN MIDLAND NATURALIST 



Pale Medici Blue and allied colors 14% 



Light Salmon Orange and allied colors 14% 



Distribution in L. Erie — localities. 



La Plaisance Cedar Prestjue 



Bay Paint Isle Bay 



Pearl Blue and allied colors 12% 



Light Salmon Orange and allied colors 25% 67% 14% 



Light Gray. Blue Viol, and allied colors.. ..50% 33% 



Medici Blue and allied colors 33% 



Light Flesh Pink and allied colors 33% 



Light Buff 8% 



Deductions from Tables of Percentages and Plate III: 



It will be immediately noted that bluish colors are more promi- 

 nent in L. Erie than in the Upper Ohio Drainage. Reddish colors 

 also tend to have lighter hues in the former. Colors of a buffy or 

 orange tone rather than pinkish, are most abundant in rivers, where 

 grayish colors also seem to predominate. The intensity of the nacre 

 color seems to diminish in the river especially going down stream. 

 Exceptions to this are in the minority. 



In the Upper Ohio Drainage: 



In Crooked Creek, Creekside, the shells are mainly light grayish 

 blue violet, but lower down at Rosston, are of a light salmon, fading 

 at a near station on Allegheny River, Kelly, to pale salmon. A 

 progressive fading out may be traced down the latter stream, as 

 well as in a tributary of the Mononghela, Dunkard Creek. The 

 shells of the Monongahela at this point are much like those of 

 Dunkard Cr. but not as red, (pale pinkish cinnamon). As the Ohio 

 is approached, the nacre becomes yellowish, (pale pinkish buff), 

 and finally fades to grayish hues. In 10 mi. Cr. at Amity, the shells 

 take on a grayish lilac hue, but at Clarksville this becomes con- 

 siderably lightened to reddish colors. In Raccoon Cr. this species 

 has a nacre color of reddish pink, at the nearest collecting point 

 in Ohio it has a yellow tinge. 



In Lake Erie: 



Presque Isle is characterized by greater proportions of salmon 

 colors. La Plaisance Bay by those of a bluish caste, Cedar Point, 

 orange. In this, as well as other species, different parts of the 



* I found no strickly pure white in this species. It seemed practically 

 negligible or is represented in the lighter allied colors of Pale Grayish Blue 

 Violet. 



