VARIATION IN EPIDERMAL COLOR IN NAJADES. 275 



Buffy Olive : ..25 % 25 % 25 % 25 %- 25 % 



Ecru Olive... 25 % 25 % 25 % 25 % 



Deductions from Tables of Percentages, etc. 



Iv. Erie shells have greater proportions of Buffs and Yellows. 

 Browns are more numerous in the Upper Ohio. 

 In the. Upper Ohio Drainage 



Shells lose their green color and become more yellowish descend- 

 ing the Allegheny. This is also mostly true of the French Creek, 

 Crooked Creek, Shenango and Mahoning Rivers. The distinction 

 is not clear cut between the Monongahela River and its Tribs. 

 but is in the case of the other rivers and their tributaries which 

 as the tables of percentages show have yellow rather than greenish 

 colors characteristic. Changes in secondary colors are also not 

 well marked. This species and L. ovata do not readily darken in 

 the river. Characteristic primary stream colors are Yellowish 

 Citrine for the Allegheny, Olive Lake for French Creek, Buffy 

 Citrine for the Shenango, Light Brownish Olive for the Mahoning. 

 In Lake Erie 



The Maumee River, (draining into L. Erie) as well as its near 



locality, La Plaisance Bay has a preponderance of buff colors. 



Presque Isle possesses more browns and olives. Chautauqua and 



Conneaut Lakes resemble Presque Isle in the distribution of color. 



Rays of Epidermis 



Simpson — "Normally showing bright rays throughout." 203 

 of 28^ shells were rayed. Fine rays were most abundant in L. Erie, 

 coarser ones in the rivers, medium ones in creeks. The oldest 

 age to which they persisted was 24 years, although such an age 

 estimated by counting the winter rings seems a little lor^g for a 

 color to persist in a mussel. Coarse rays were most abundant 

 in male shells, fine in females. They persisted in all ages of 

 the animals. 



Relation of Epidermal Color to Estimated Age of Animals. 



Juveniles are Yellow or Greenish Yellow, percentages of the former 

 decreasing, that of the latter increasing with age. Greenish Yellow 

 is perhaps always the more abundant color. Browns and blacks 

 appear as early as the estimated loth year in the Upper Ohio, 

 and somewhat earlier in L. Erie. "Old age" colors as a rule are 

 not abundant in this or in the following species. No color or group 

 of colors seemed peculiar to any given age. 



