Bull. U. S. B. F. (No. 1103.) 
Figure 1. — Right valve, 7.73 centimeters in length, of a 7-year-old Lake Pepin mucket, Lampsilis silquoiden 
pepinensis Baker (Lampsilis luteola, of authors), illuminated to show major interruption rings, i. e., 
annual growth rings 
Figure 2. — Male (left) and female (right) specimens of yellow sand shell, Lampsilis ancdontoides (Lea), Mississippi River, 
Fairporl, Iowa. Upper male, 11.48 centimeters; lower male, 10.12 centimeters; upper female, 11.79 centimeters; lower 
female, 12.36 centimeters in length 
