VARIATION IN EPIDERMAL COLOR OF NAJADES. 259 



from L. Erie are green. L. Erie shells have also a larger proportion 

 of green with advancing age. Shells in both become black and 

 brownish with age, but in L. Erie later than in the Upper Ohio. 

 These old age colors appear at 4 years and are complete at 9. 

 No one color or group of colors was found to be peculiar of any age. 



Observation on Sex-Correlative Coloration as Related to Epidermal 



Color {11 Shells.) 

 Young males are of a Buffy Olive color, becoming reddish brown 

 with age. Females in youth are of a Yellowish Olive hue, becoming 

 brownish red with age and tending to blacken. 



3. — Elliptio dilatatus 



Dull green, young shells Buffy Citrine, Yellowish Citrine 



Yellowish brown Bister, Warm Sepia, Dresden Brown, Ani- 



Darker, when old. line Black, Chestnut, Cinnamon. 



Distribution of Colors as a Whole in Upper Ohio Drainage and 

 L. Erie. (561 shells.) 



Bister . - -30% 



Warm Sepia - 20% 



Dresden Brown . 20% 



Buffy Citrine ' 20% 



Aniline Black ' 10% 



Distribution of Colors as a Whole in the Upper Ohio Drainage 

 (509 shells). 



Bister 20% 



Warm Sepia - j- - -2o% 



Dresden Brown 20% 



Dresden Brown... 20% 



Seal Brown : 20% 



Brownish Olive 20% 



Distribution of Colors as a Whole in Upper Ohio Tributaries etc. 



Alle'nv Alle'ny Mon'g Mon'g Ohio Beaver Beaver 



Tribs. River Tribs. River River Tribs. River 



Bister 22%......40% :25%......50%......25% 12% 



Warm Sepia 27% 20%......i2%.... 25%......30% 25% 



Dresden Brown .22 7o. 40% 25% 12%. 25% 



Seal Brown. 29% 25% 25% 12%... 



Brownish Olive. 2,7%--50% -33% 5o% 



Distribution of Colors as a Whole in L. Erie (52 shells). 



Chestnut Brown .....30% 



Dresden Brown 20% 



Cinnamon Brown 20% 



Yellowish Citrine 20% 



Aniline Black , 10% 



