U. S. B. F.— Doc. 781. 



Plate I. 



FIG. 1— TRUNCILLA WALKERI, NEW SPECIES. 

 Upper figures, females; lower figures, males. 



FIG. 2.— THE GREAT FALLS OF THE CUMBERLAND, 85 FEET HIGH, A BARRIER TO THE ASCENT OF 



FISH AND MUSSELS. 



