228 THE AMERICAN MIDLAND NATURAUST 



Distribution of Colors as a Whole in L. Erie (30 shells). 



Pearl Blue, etc 33% 



Pale Pinkish Lilac, etc 41 % 



Pale Congo Pink, etc 20 % 



Distribution in L. Erie — Localities. 



Presque La Plaisance 



Isle Bay 



Pearl Blue, etc 30% 16% 



Pale Pinkish Lilac, etc 50% 50% 



Pale Congo Pink, etc , 13% 33% 



Deductions from Tables of Percentages and Plate III. 



There is a greater percentage of pearl blue in L. Erie, and there 

 are more reddish shells in the Upper Ohio Drainage. 

 In the Upper Ohio Drainage: 



Less Pearl Blue and more of the reddish colors are present in the 

 Allegheny River. Shades tending toward purplish predominate in 

 the Ohio. Shells of this species lighten in color going down the 

 Allegheny and Ohio, at least in the upper stretches of the latter. 



In Lake Erie: 



Presque Isle possesses more pearl blues and less pink than La 

 Plaisance Bay. 



Observation on Sex Correlative Coloration, etc. (5 shells). 



The males appear to have lighter lilac and pinkish shades. 



8. — Propter a alata 



SIMPSON RIDGEWAY 



Coppery purple. Hydrangea Pink, Light Pinkish Lilac, Light 



Purplish Vinaceous, Light Russet Vinaceous, 

 Light Purplish Lilac. 



Distribution of Color in Upper Ohio Drainage and Lake Erie as 

 a Whole. (55 shells). 



Hydrangea Pink, etc : 27% 



Light Pinkish Lilac, etc , 34% 



Light Purplish Vinaceous, etc 21 % 



Light Russet Vinaceous, etc 16 % 



Distribution of Colors as a Whole in Upper Ohio Drainage. (24 

 shells). 



Hydrangea Pink, etc 27% 



Light Purplish Vinaceous, etc 46 % 



Light Russet Vinaceous, etc — 24 % 



Light Pinkish Lilac „ , 3 % 



