VARIATION IN NACREOUS COLOR OF NAIADES 217 



arrangement adopted, but varieties of the hues given in the tables, 

 on "Distribution of Colors as a Whole in the latter of which, 

 effort is made to throw light on the first problem stated. There 

 then follows tables of percentages giving the relative distribution 

 of colors in the Upper Ohio Drainage as a whole, and separately, 

 its component drainages. The same is done for Lake Erie and its 

 various collecting stations. After remarks largely in explanation 

 of outstanding points of Plate III, (chart illustrating sequence 

 of nacreous color changes; Problem IIL, the discussion of each 

 species terminates with the evidence for possible association of 

 Sex Correlative Coloration with the nacreous color of the shell. 



I. — Fuscofiaja flava. 



SIMPSON RIDGEWAY 



White to Pearl blue, Pale Grayish Blue Violet, Pale Medici Blue 



Salmon; Pale Pinkish Cinnamon, Pale Pinkish Buff, Light Flesh 



Pink. 

 Rose tinted. Light Orange Pink, Light Salmon Orange. 



Distribution of Colors as a Whole in Upper Ohio Drainage and 

 L. Erie. (273 shells.) 



Pale Pinkish Cinnamon and allied colors 21% 



Pale Pinkish Buff and allied colors 13% 



Light Orange Pink and allied colors... ...11% 



Pale Grayish Blue Violet and allied colors 25% 



Pearl Blue and allied colors -io% 



Distribution of Colors as a Whole in Upper Ohio Drainage. 



(225 shells) 



Pale Pinkish Cinnamon and allied colors 27% 



Pale Pinkish Buff and aUied colors 23% 



Light Orange Pink and allied colors 16% 



Pale Grayish Blue Violet and allied colors 17% 



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



Alle'ny Alle'ny Mon'g. Mon'g. Ohio Ohio Tusca. 

 Tribs. River Tribs River Tribs. River River 



Pale Pink. Cinnamon, etc .30%....: 62%.... 27%. .100%.. ..30% 



Pale Pink. Buff, etc 25 %....67 % .....23 %... ......25 7o--50% 



Light Orange Pink, etc ..20%.... -50% 20% 



Pale Gray. Blue Violet, etc 13% -33% 50% 



Pale Gray Lavender, etc 25 % 



Deeper Hermosa Pink 25 % 



Distribution of Colors as a Whole in L. Erie. (67 shells). 



Peajl Blue and allied colors 18% 



Light Flesh Pink and allied colors 18% 



Pale Gray. Blue Violet and allied colors 14% 



