VARIATION IN EPIDERMAL COLOR OF NAJADES. 269 



Aniline Black .'. 20% 



Snuff Brown. 10% 



Saccardos Umber 10% 



Distribution of Colors as a Whole in Upper Ohio Tributaries. 



Alle'vy Riv. Monong. Riv. Ohio Riv. 



Olive 25%... 25% 



Mummy Brown 50% 25% 



Buffy Olive 25% 



Aniline Black 25% 25% 



Snuff Brown^ 25 % ....25 % 25 % 



Saccardos Umber 25% 



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



Light Brownish Olive 30% 



Buffy Citrine 20% 



Buffy Olive..... : -20% 



Mummy Brown 20% 



Dresden Brown .". i°% 



Distribution in L. Erie— lyocalities. 



Cedar Presque Maumee 



Point Isle River 



Light Brownish Olive 25 % .25 %.... 



Buffy Citrine 25 % 25 % 25 % 



Buffy Olive :-25% 25% 



Mummy Brown 25 % 25 % 25 % 



Dresden Brown... 25% 25% 



Deductions from Tables of Percentages and PI. III. 



In this species also it is noted that the colors of the shells from 

 the Upper Ohio Drainage are darker. The browns of L. Erie are 

 of reddish hues, those from the Upper Ohio Drainage more blackish 

 in nature. L. Erie has also a larger percentage of olive colors. 

 In the Upper Ohio Drainage 



A darkening of colors from olive to brown may be traced down 

 the Allegheny and in primary colors, (olive to brown), from the 

 Monongahela into the Ohio. Darkening from Brown to Blackish 

 is characteristic of a large part of the Ohio. Saccardos Umber 

 would be a secondary color for the Allegheny; Buff}' Olive for the 

 Ohio. Other characteristic colors are indicated in the tables given 

 above. 

 In Lake Erie ^ 



Here the shells possess a brownish olive not found in the shells of 

 the Maumee River which empties into it. Buffy Olive colors are 

 peculiar to Cedar Point shells, while the deeper browns belong to 

 Presque Isle shells. 



