Bull. U. vS. B. F., 1917-18. 



Plati^ XXVI. 



I'^^'f^^W^ 



Upper: Paper-shell, Anodonta suborbiculata (Say). (See p. .55) 



Lower pair: Spectacle-case, Margaritana monodonta (Say), from Mississippi River. (See p. .35) 



The three small shells in upper left-hand corner of plate are examples of Sphceriidae, not fresh-water mussels. 



