230 THE AMERICAN MIDLAND NATURALIST 



Pearl Blue, etc 25% 



Lavender, etc.._ 23% 



Grayish Blue Violet, etc 22 % 



Distribution of Colors as a Whole in the Upper Ohio Drainage. 

 (45 shells). 



Pearl Blue, etc 23% 



Pale Aniline Lilac, etc.._ 20% 



Lavender, etc 22% 



Light Grayish Blue Violet, etc 28% 



Distribution of Colors in the Upper Ohio Tribs., etc. 



.4 llegheny Beaver 



Tribs. Tribs. 



Pearl Blue, etc _ 14% 20% 



Pale Aniline Lilac, etc 57 % 15 % 



Lavender, etc 25% 



Light Grayish Blue Violet, etc 29% 40% 



Distribution of Colors as a Whole in Lake Erie. (24 shells) 



Pale Aniline Lilac, etc 31 % 



Pearl Blue, etc 25% 



Pale Grayish Blue Violet, etc 19% 



Lavender, etc.._ 25% 



Distribution in L. Erie — Localities. 



Presque Maumee Conneaut 



River River Creek 



Pale Aniline Lilac, etc.._ 33 % 25 % 28 % 



Pale Blue, etc 25 % 25 % - 14% 



Pale Grayish Blue Violet, etc 23% 20% 43% 



Lavender, etc.._ 15% 25% 14% 



Deductions from Tables of Percentages and PI. III. 

 There are more pearl blue, lilac and their related colors in L 

 Erie than in the Upper Ohio Drainage, but there are less of a 

 lavender hue. 



In the Upper Ohio Drainage: 



Lilac colors appear to predominate in the Allegheny Tributaries 

 as against lavender in the Beaver Tribs. Conneaut Creek draining 

 into L. Erie possesses more pearl blue shells than either the Beaver, 

 Shenango, or Allegheny Rivers. Descending French Creek, the 

 nacre of the species appears to lighten. Pale grayish Blue Violet is 

 characteristic of the French Creek, while Pearl Blue is more typical 

 of the Shenango. 



In Lake Erie: 



Presque Isle stands out for lilac colors; the Maumee River 

 which drains into it, possesses a great deal of lavender. 



