223 



Kig. SO 



1. Anterior view of Teredo navaiis, showing relations of shell and foot. The translucent marginal 

 web of tissue encircling the aperture of the shell is the inner free fold of the mantle, x 10. 



2. Detail of surface sculpture of the shell of Teredo navaiis, in the region of the angle formed by 

 the juncture of the finely serrate ridges of the anterior lobe (left) with the coarsely denticulate ridges 

 of the anterior median area (right), x 50. 



