VARIATION IN NACREOUS COLOR OF NAIADES 229 



Distributior in Upper Ohio Tributaries. 



Alle'tiy Riv' Monong. Riv. Ohio Riv. 



Light Purplish Vinaceous, etc... 60% 60% 33% 



Light Russet Vinaceous, etc 30 % 40% 33 % 



Hydrangea Pink, etc 10% -33% 



Distribution of Colors as a Whole in L. Erie (31 shells). 



Hydrangea Pink, etc 25% 



Light Purplish Lilac, etc 50% 



Grayish Vinaceous, etc 25% 



Distribution in L. Erie — Localities. 



La Plaisance Cedar Presque 



Bay Point Isle 



Hydrangea Pink, etc 67% 16% 12% 



Light Purplish Vinaceous, etc 3>3% 11% - 44% 



Light Purplish Lilac, etc _ 58 %. 44% 



Deductions from Tables of Percentages and PI. III. 



Lake Erie shells appear to be of a more uniform lilac hue, while 

 there is a greater proportion of pinks and purples in the Upper Ohio 

 Drainage. 

 In the Upper Ohio Drainage: 



The nacreous color seems to be lighter in the Ohio than either 

 the Allegheny or the Monongahela. Coppery purple, (Light Russet 

 Vinaceous), is most prominent in the Monongahela. A tendency 

 to lighten going down stream is seen in the Allegheny. 

 In Lake Erie: 



La Plaisance Bay stands out for a greater proportion of pinks, 

 Cedar Point for Lilac purple, and Presque Isle for dark purple colors. 



Observation on Sex Correlative Coloration, etc. (6 shells). 

 Males — pinkish or lilac. 

 Females — purple or russet. 



9. — Anodontoides ferrussacianus. 



Here the general tone of the nacre color — not merely the irides- 

 scence — was considered. 



SIMPSON RIDGEWAY 



Bluish-white Lavender, Grayish Blue Violet, Pale Grayish 



Blue Violet 

 Bluish Pearl Blue, Pale Aniline Lilac. 



Distribution of Colors as a Whole in the Upper Ohio Drainage 

 and Lake Erie. (69 shells). 

 Pale Aniline Lilac, etc 26 % 



