2-]2 THE AMERICAN MIDLAND NATURALIST 



Relation of Epidermal Colors to Estimated Age of Animals. 



Bluish green is most common in young shells, decreasing with 

 age when the shells become brown, which may be an early as the 

 4th or 5th year. Old age colors may appear completely at 6. A 

 brownish deposit occurs on L. Erie shells of this and other species 

 which at times is apt to confuse the observer as to the true color. 

 No color or group of colors seemed peculiar to any given age. 



Observation on Sex-Correlative Coloration as associated with Epider- 

 mal Color. (4 shells). 

 Males — brownish or Yellowish Olive. 

 Females — green . 



10. — Eurynia recta 



SIMPSON RIDGEWAY 



Black Bister 



Olive Green Olive, Brownish Olive, Dark Greenish Olive 



Other colors noted: (browns) Warm Sepia, 

 Snuff Brown, Mummy Brown. 



Distribution of Colors as a Whole in Upper Ohio Drainage and 

 L. Erie (54 shells). 



Olive - - 30% 



Warm Sepia.. -*— 20% 



Snuff Brown..... ..— 20% 



Bister ._ .20% 



Brownish Olive .10% 



Distribution of Colors as a Whole in Upper Ohio Drainage 

 (33 shells). 



Mummy Brown. ...30% 



Olive 20% 



Snuff Brown 20% 



Warm Sepia — 10% 



Brownish Olive . iQ% 



Dark Greenish Olive ..-.. 10% 



Distribution of Colors as a Whole in Upper Ohio Tributaries. 



Allegheny Allegheny Ohio Tuscarawas 

 Tribs. River River River 



Mummy Brown 16% 20% 



Olive 16% 25% 20% 



Snuff Brown .16% 25% 20% 



Warm Sepia 16% 25% 20% 



Brownish Olive.. 12% 20% 50% 



Dark Greenish Olive 32% ...12% 50% 



Distribution of Colors as a Whole in L. Erie — Localities. 

 Phestnut , ,.-.20% 



