Bull. U. S. B. F., 1921-22. (Doc. 922.) 



Fig. 2o5. — A crimp of living mussels whose shells are encrusted with Bryozoa, barnacles, sea anemonies, ami serpulids 



Fui. 207. — Vertical view oJ mussels on a natural lied, showing the characteristic position they assume with the anterior 

 end buried in the sand and the posterior or syphon end projecting well above the level oi the bottom. 



