VARIATION IN NACREOUS COLOR OF NAIADES 223 



Distribution of Colors as a Whole in Upper Ohio Drainage and 

 L. Erie. (263 shells). 



Pearl Blue and allied colors 44% 



Pale Vinaceous Pink and allied colors.... 18% 



Venetian Pink and allied colors 20% 



Light Ochraceous Salmon and allied colors >. 8% 



Distribution of Colors in Upper Ohio Drainage (247 shells). 



Pearl Blue with allied colors. 48% 



Venetian Pink with allied colors ...30% 



Pale Vinaceous Pink and allied colors 14% 



Light Ochraceous Salmon and allied colors 8% 



Distribution of Colors in Upper Ohio Tributaries etc. 



Alle'ny Alle'ny Beaver Beaver 



Tribs. River Tribs. River 



Pearl Blue and allied colors 63% .-27% 30% 46% 



Venetian Pink and allied colors 10% 33% 31% 38% 



Pale Vinaceous Pink and all col 7% 19% ^3% 



^ Light Ochraceous Salmon & all col 14%.. 1 1 %- 20% 15% 



Distribution of Colors as a Whole in L. Erie, 



Pale Vinaceous Pink and allied colors.. 45% 



Burn Blue and allied colors 33% 



Orange Pink and allied colors .- ....16% 



Light Pearl Blue and allied colors 4% 



Distribution in L. Erie — Localities. 



PresQue Isle La Plaisance 

 Bay Bay 



:pale Vinaceous Pink, etc. 66% 



Burn Blue, etc .-... 88% 



Orange Pink, etc 14% 



Light Pearl Blue, etc .....11 % 



Deductions from Tables of Percentages and PI. III. 



Pearl blue as such is more abundant in the Upper Ohio Drainage, 

 but to explain this apparent discrepancy to the tendencies already- 

 observed, it may be pointed out that there are larger percentages 

 of bluish colors in L. Erie than in the Upper Ohio, furthermore 

 the more or less lilac shades of L. Erie shells show admixture with 

 bluish tints. 

 In the Upper Ohio Drainage: 



Pearl blues are found to greater extent in the rivers than in their 

 tributaries, where the colors are pink and reddish. Fading out 

 tendencies are observed in the Allegheny River and French Creek. 

 At the nearest station to the Allegheny River in French Creek they 

 are pinkish, while in the Allegheny itself they are grayish blue. 



