PLATE 13. 
FEU ait Mone) GVaIBAC WIRING EDITaIaD ce one DIAC Noa a ee att 
a. Interior view of the lower valve in its natural posture when ad- 
herent to a foreign body, the front side being much higher than 
the other; natural size. 
b. View of the front side of the same, the right-hand border of the 
figure being that of the adherent surface of the valve. 
ce. Upper valve; exterior surface. 
d. Interior surface of the same. 
