Bull. U. S. B. F., 1919-20. 



Plativ XI. 



Fio. I.— Aufflaize River near Defiance. Ohio, showing 

 islets and pools cuutaiumg dense beds of mussels. 



Fig. 2. — Maumce River, Defiance Ohio. The river 

 bed a broad valley with limestone bottom, broken 

 into numerous pools and channels with little islands 

 — an excellent growth of fresh-water mussels. 



Fig. 3. — The draining of the Feeder Canal near Fort 

 Wayne, Ind., revealed a remarkably dense popula- 

 tion of fresh-water mussels. 



Fig. 4,— Parts of the Miami and Erie Canal afford 

 excellent environments for mussels. 



Fig 



-Construction of wing dams in the upper Mississippi River often renders condittnus uul.i 

 previously throve in such sections of the river. 



