268 THE AMERICAN MIDLAND NATURALIST 



Rays of Epidermis 

 Simpson "Often rayless, sometimes feebly rayed". 37 of 58 

 shells were rayed, the oldest age being 13. The texture of these 

 from the lake was prevailingly fine those of the rivers medium. 

 The~most common color was a Dark Green. 



Relation of Epidermal Colors to Estimated Age of Animals. 



In youth, 1-2 of the shells are either Brown or Green. Most have 

 J^ecome of a greenish hue about the 7th year. Green is more promi- 

 nent in L. Erie shells. Old age colors may appear at 6, completely 

 at 14 years. There appeared to be few if any completely dark 

 colored specimens. No colors seemed to be peculiar to any given age. 



Observation on Sex-Correlative Coloration as Associated with Epider- 

 mal Color. (5 shells). 

 In the small amount of L. Erie material only green colors seemed 

 to characterize males, yellow, females. 



8. — Propter a alata 



SIMPSON ' RIDGEWAY 



Brownish Mummy Brown, Buffy Brown, Bister, Light 



Blackish Brownish Olive 



Olive Green Buffy Citrine, Buffy Olive 



Reddish Dresden Brown. 



Distribution of Colors as a Whole in Upper Ohio Drainage and 

 L. Erie (55 shells). 



Buffy Citrine 30% 



Mummy Brown 20% 



Buffy Brown... .-... 20% 



Bister 20% 



Buffy Citrine.... .-.10% 



Distribution of Colors as a Whole in Upper Ohio Drainage (24 

 shells). 



Olive 20% 



Mummy Brown •. 20% 



Buffy Olive.. --20% 



Aniline Black 20% 



Snuff Brown. 10% 



Saccardos Umber 10% 



Distribution of Colors as a Whole in Upper Ohio Drainage 

 (24 shells). 



Olive : ...20% 



Mummy Brown 20% 



Buffy Olive... 20% 



