270 THE AMERICAN MIDLAND NATURALIST 



Rays of Epidermis 

 Simpson mentions no rays in this species. However34of 55 shells 

 were found to be rayed, and rays persist at least until the 15th year. 

 In this case, lake shells had coarser rays than those of the river, 

 although there were a large number of fine rayed specimens in 

 both. Light green was the prevailing color. 



Relation of Epidermal Color to Estimated Age of Animal. 



The percentages of green colors tend to increase with age in 

 both Upper Ohio and L. Erie, while brown, the other juvenile 

 color, decreases with age. Color changes take place about the 12th- 

 14th year, old age colors may appear as early as 10 years, more 

 fully at 12. Blacks apparently decrease with age in the Upper 

 Ohio, but this is based on fragmentary data. No color or group of 

 colors seemed peculiar to any given age. 



Observation on Sex-Correlative Coloration as related to Epidermal 



Color. (5 shells). 



Males are more largely green, females brownish yellow. 



9 . — A nodonloid'es ferussacianns 



SIMPSON , • RIDGEWAY" 



Greenish Hellebore green; other colors: Buflfy Olive 



Brownish Olive, Yellowish Olive, Deep Olive 

 Isabella Color. 



Distribution of Colors as a Whole in Upper Ohio Drainage and 

 L. Erie (69 shells). 



Buffy Olive- : -.-30% 



Brownish Olive — - 20% 



Yellowish Olive ,. 20% 



Deep Olive 20% 



Olive 10% 



Distribution of Colors as a Whole in Upper Ohio Drainage 

 (45 shells. 



Buffy Citrine .— 30% 



Brownish Olive - 20% 



Isabella Color ....'.... » 20% 



Hellebore Green... 20% 



Buffy Olive 10% 



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



Alle'ny Beaver 



Tribs. Tribs. 



Buffy Citrine 20% 20% 



Brownish Olive ..60%..... ....—....20% 



