VARIATION IN EPIDERMAL COLOR IN NAJADES. 257 



Relation of Epidermal Color to Estimated Age of Animals. 



Young shells of this species in the Upper Ohio Drainage are 

 mostly Yellowish Brown; in L. Erie, mostly Brownish Green. 

 In the former they become brownish or black rapidly as early as 

 the 3rd and after the 5th-8th year, where in my material yellowish 

 brown, was represented in only 1-8 of the shells. Yellowish brown 

 and brown were nearly equally represented in L. Erie shells. No 

 one color or group of colors seemed peculiar to a given age except 

 the deep browns and blacks of old age or advanced maturity. 



Observation on Sex Correlative Coloration as Related to Epidermal 



Color. 

 Older males are characterized by a Seal Brown color, younger 

 by more of a greenish yellow. Females have larger proportions of 

 more vivid Reddish Brown colors, while the younger ones tend 

 toward BufTy Olive Colors. ^ 



2 — Amblema costata 



SIMPSON RIDGEWAY 



Yellowish green Yellowish Olive. Yellowish Citrine, Dull 



Citrine. 

 Brown or blackish Bister, Mars Brown, Prouts Brown, Dresden 



Brown 



Distribution of Colors as a Whole in Upper Ohio Drainage and 

 Iv. Erie (185 shells). 



Yellowish Olive -.- ^- --40% 



Prouts Brown .- — 20% 



Mars Brown ^ — - -2o% 



Dresden Brown _ 10% 



Bister. -- 10% 



Distribution of Colors as a Whole in Upper Ohio Drainage 

 (107 shells). 



Prouts Brown 3°% 



Yellowish Citrine -- 20% 



Dresden Brown 20% 



Bister.... -.. .-20% 



BuflFy Citrine .-.10% 



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



Alle'ny Alle'ny Beaver Beaver Ohio 



Tribs. River Tribs. River River 



Prouts Brown 40% -60% 32% 33% 25% 



Yellowish Citrine. 20% --37%---33% - 



Dresden Brown .40%.... 12% 50% 



Bister 40% 6%. .25% 



Buffy Citrine .,...,. 12 % 2>3 % 



